Strange behaviour creating a multipolygon with utilsplugin2

[hsonesson@…]

What steps will reproduce the problem?

1. Open the attached OSM-file.
2. Select the two buildings.
3. Press Shift + J

What is the expected result?

They should become a multipolygon.

What happens instead?

The become a scramble of building fragments and JOSM throws an error.

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

I'm using utilsplugin2, and I'm running it on Windows 10.

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2017-01-02 00:53:29 +0100 (Mon, 02 Jan 2017)
Build-Date:2017-01-02 02:33:21
Revision:11427
Relative:URL: ^/trunk

Identification: JOSM/1.5 (11427 da) Windows 10 64-Bit
Memory Usage: 247 MB / 247 MB (65 MB allocated, but free)
Java version: 1.8.0_111-b14, Oracle Corporation, Java HotSpot(TM) Client VM
Screen: \Display0 1920x1080
Maximum Screen Size: 1920x1080
VM arguments: [-Djava.security.manager, -Djava.security.policy=file:<java.home>\lib\security\javaws.policy, -DtrustProxy=true, -Djnlpx.home=<java.home>\bin, -Djnlpx.origFilenameArg=%UserProfile%\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\56\1ee8cfb8-675226d5, -Djnlpx.remove=false, -Djava.util.Arrays.useLegacyMergeSort=true, -Djnlpx.splashport=62810, -Djnlp.application.href=https://josm.openstreetmap.de/download/josm.jnlp, -Djnlpx.jvm=<java.home>\bin\javaw.exe, -Djnlpx.vmargs=LURqYXZhLnV0aWwuQXJyYXlzLnVzZUxlZ2FjeU1lcmdlU29ydD10cnVlAC1Eam5scC5hcHBsaWNhdGlvbi5ocmVmPWh0dHBzOi8vam9zbS5vcGVuc3RyZWV0bWFwLmRlL2Rvd25sb2FkL2pvc20uam5scAA=]
Dataset consistency test: No problems found

Plugins:
+ buildings_tools (33004)
+ utilsplugin2 (33088)
+ wikipedia (33098)

Last errors/warnings:
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: JCS - Silent failure during download: {0}
- E: Handled by bug report queue: org.openstreetmap.josm.tools.JosmRuntimeException: Join areas internal error.
- E: Handled by bug report queue: org.openstreetmap.josm.tools.JosmRuntimeException: Join areas internal error.


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

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-2 (54) of javawsApplicationThreadGroup
org.openstreetmap.josm.tools.JosmRuntimeException: Join areas internal error.
	at org.openstreetmap.josm.actions.JoinAreasAction.findBoundaryPolygons(JoinAreasAction.java:1170)
	at org.openstreetmap.josm.actions.JoinAreasAction.joinAreas(JoinAreasAction.java:647)
	at org.openstreetmap.josm.actions.JoinAreasAction.join(JoinAreasAction.java:532)
	at org.openstreetmap.josm.actions.JoinAreasAction.actionPerformed(JoinAreasAction.java:462)
	at javax.swing.SwingUtilities.notifyAction(Unknown Source)
	at javax.swing.JComponent.processKeyBinding(Unknown Source)
	at javax.swing.KeyboardManager.fireBinding(Unknown Source)
	at javax.swing.KeyboardManager.fireKeyboardAction(Unknown Source)
	at javax.swing.JComponent.processKeyBindingsForAllComponents(Unknown Source)
	at javax.swing.JComponent.processKeyBindings(Unknown Source)
	at javax.swing.JComponent.processKeyEvent(Unknown Source)
	at java.awt.Component.processEvent(Unknown Source)
	at java.awt.Container.processEvent(Unknown Source)
	at java.awt.Component.dispatchEventImpl(Unknown Source)
	at java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.awt.Component.dispatchEvent(Unknown Source)
	at java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source)
	at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source)
	at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source)
	at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source)
	at java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source)
	at java.awt.Component.dispatchEventImpl(Unknown Source)
	at java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.awt.Window.dispatchEventImpl(Unknown Source)
	at java.awt.Component.dispatchEvent(Unknown Source)
	at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.awt.EventQueue.access$500(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue$4.run(Unknown Source)
	at java.awt.EventQueue$4.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)

[anonymous]

This is the OSM-file before I press Shift + J

[anonymous]

Screenshot before

[anonymous]

Screenshot after

[Don-vip]

Closed as duplicate of #10511.