conflict created in Relation Editor when replacing one oneway road with another

[Polyglot]

What steps will reproduce the problem?

1. use routing assistant near roundabout
2. in previous step oneway part of fork before roundabout was removed, that went well
3. Then it added the proper part of the fork, which seems to work as well.
4. Error appears
5. Relation editor has both save and refresh button highlighted.

What is the expected result?

What happens instead?

Please provide any additional information below. Attach a screenshot if possible.

Build-Date:2018-07-13 20:39:51
Revision:14027
Is-Local-Build:true

Identification: JOSM/1.5 (14027 SVN en) Linux Mint 18.3 Sylvia
Memory Usage: 1479 MB / 1733 MB (185 MB allocated, but free)
Java version: 1.8.0_171-8u171-b11-0ubuntu0.16.04.1-b11, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: :0.0 1600x900
Maximum Screen Size: 1600x900
Java package: openjdk-8-jre:amd64-8u171-b11-0ubuntu0.16.04.1

Dataset consistency test:
[NO DATASET] {Way id=-2355259 version=0 VT> nodes=[{Node id=1794049286 version=3 V lat=-33.9145818,lon=151.1429014}, {Node id=5625183768 version=1 V lat=-33.9145884,lon=151.1429256}, {Node id=5625183768 version=1 V lat=-33.9145884,lon=151.1429256}, {Node id=1794049290 version=3 V lat=-33.9146018,lon=151.1429454}, {Node id=1794049290 version=3 V lat=-33.9146018,lon=151.1429454}, {Node id=1794049292 version=3 V lat=-33.9146202,lon=151.142958}, {Node id=1794049292 version=3 V lat=-33.9146202,lon=151.142958}, {Node id=5625183767 version=1 V lat=-33.9146391,lon=151.1429618}, {Node id=5625183767 version=1 V lat=-33.9146391,lon=151.1429618}, {Node id=1794049296 version=3 V lat=-33.9146581,lon=151.142958}, {Node id=1794049296 version=3 V lat=-33.9146581,lon=151.142958}, {Node id=5625183766 version=1 V lat=-33.914675,lon=151.1429468}, {Node id=5625183766 version=1 V lat=-33.914675,lon=151.1429468}, {Node id=1794049300 version=3 V lat=-33.9146879,lon=151.1429297}]} is referenced by {Relation id=4524022 version=34 MVT [way 475416345, way 173962126, way 324785014, way 459308078, way 288153522, way 475416346, way 152429518, way 152539538, way 152539539, way 261016362, way 288149860, way 324785015, way 405801544, way 150571050, way 150572347, way 150572342, way 365936267, way 150573807, way 507279788, way 414320657, way 569701334, way 569701333, way 172906156, way 574562338, way 574562339, way 172906120, way 172906142, way 172906116, way 172906158, way 172842998, way 324785027, way 180087041, way 324785026, way 183248420, way 174123847, way 589063931, way 173323608, way 161491733, way 567594038, way 173323609, way 383228998, way 24018020, way 463192288, way 174125102, way 183499035, way 172918071, way 168097078, way 589063920, way -2355259, way 168097079, way 589063923, way 172918069, way 183497679, way 183497678, way 172918047, way 173633978, way 173633965, way 362357320, way 291754773, way 291754774, way 324785020, way 385523676, way 173633966, way 385523783, way 324785029, way 173633976, way 574202825, way 173633960, way 324785018, way 173309340, way 173309344, way 172944904, way 383218780, way 383218781, way 2664397, way 24256324, way 4786954, way 46739826, way 170818679, way 385523762, way 385523768, way 385523765, way 385523759, way 45415387, way 170818682, way 286360952, way 382412067, way 382412068, way 286360951, way 286360950, way 286360949, way 286360948, way 290327881, way 286361438, way 47518048, way 170888275, way 175260613, way 290327879, way 290327880, way 286360557, way 324785016, way 175974423, way 215320362, way 215320364, way 219617203, way 242582514, way 172302241, way 503698395, way 574814030, way 324785025, way 574612502, way 574612501, way 302983253, way 247956389, way 169911706, way 411198554, way 247981349, way 280415585, way 169912132, way 169912128, way 287833281, way 247956390, way 600520756, way 485292137, way 252123445, way 407224857, way 407224855, way 169912745, way 169913413, way 373111044, way 482964818, way 169913411, way 77350940, way 245266111, way 245021282, way 34695430, way 324785034, way 478243190, way 527690683, way 5011713, way 514975265, way 527690684, way 129087878]} but not found in dataset


Plugins:
+ Mapillary (v1.5.15)
+ OpeningHoursEditor (34389)
+ apache-commons (34389)
+ apache-http (34389)
+ buildings_tools (34212)
+ ejml (34389)
+ geotools (34125)
+ jts (34206)
+ measurement (34206)
+ opendata (34389)
+ pt_assistant (306)
+ reverter (34271)
+ scripting (30785)
+ tag2link (34109)
+ terracer (34109)
+ todo (30305)
+ utilsplugin2 (34389)
+ wikipedia-dev (v1.0.1-43-gb77c0c5)

Tagging presets:
+ https://josm.openstreetmap.de/josmfile?page=Presets/BENELUX&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/Trees&zip=1
+ https://josm.openstreetmap.de/josmfile?page=Presets/OneClick&zip=1

Map paint styles:
+ https://josm.openstreetmap.de/josmfile?page=Styles/PublicTransport&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/NumberedCycleNodeNetworks&zip=1

Last errors/warnings:
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: Unsaved changes - <html>The relation has been changed.<br><br>Do you want to save your changes?</html>
- E: Handled by bug report queue: org.openstreetmap.josm.data.osm.DataIntegrityProblemException: Relation member must be part of the same dataset as relation(relation 4524022, way -2355259)


=== REPORTED CRASH DATA ===
BugReportExceptionHandler#handleException:
No data collected.

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-0 (18) of main
org.openstreetmap.josm.data.osm.DataIntegrityProblemException: Relation member must be part of the same dataset as relation(relation 4524022, way -2355259)
	at org.openstreetmap.josm.data.osm.Relation.checkMembers(Relation.java:470)
	at org.openstreetmap.josm.data.osm.Relation.fireMembersChanged(Relation.java:488)
	at org.openstreetmap.josm.data.osm.Relation.setMembers(Relation.java:59)
	at org.openstreetmap.josm.data.osm.Relation.cloneFrom(Relation.java:243)
	at org.openstreetmap.josm.command.ChangeCommand.executeCommand(ChangeCommand.java:65)
	at org.openstreetmap.josm.data.UndoRedoHandler.addNoRedraw(UndoRedoHandler.java:234)
	at org.openstreetmap.josm.data.UndoRedoHandler.add(UndoRedoHandler.java:262)
	at org.openstreetmap.josm.gui.dialogs.relation.actions.SavingAction.applyExistingNonConflictingRelation(SavingAction.java:104)
	at org.openstreetmap.josm.gui.dialogs.relation.actions.SavingAction.applyChanges(SavingAction.java:177)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction$OKActionPTEditor.actionPerformed(MendRelationAction.java:1849)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction.getNextWayAfterSelection(MendRelationAction.java:1469)
	at org.openstreetmap.josm.plugins.pt_assistant.actions.MendRelationAction$4.keyPressed(MendRelationAction.java:1180)
	at java.awt.Component.processKeyEvent(Component.java:6491)
	at javax.swing.JComponent.processKeyEvent(JComponent.java:2832)
	at java.awt.Component.processEvent(Component.java:6310)
	at java.awt.Container.processEvent(Container.java:2238)
	at java.awt.Component.dispatchEventImpl(Component.java:4889)
	at java.awt.Container.dispatchEventImpl(Container.java:2296)
	at java.awt.Component.dispatchEvent(Component.java:4711)
	at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1954)
	at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:835)
	at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1103)
	at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:974)
	at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:800)
	at java.awt.Component.dispatchEventImpl(Component.java:4760)
	at java.awt.Container.dispatchEventImpl(Container.java:2296)
	at java.awt.Window.dispatchEventImpl(Window.java:2746)
	at java.awt.Component.dispatchEvent(Component.java:4711)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:760)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
	at java.awt.EventQueue$4.run(EventQueue.java:733)
	at java.awt.EventQueue$4.run(EventQueue.java:731)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:730)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)