JOSM unresponsive after using WMS

[nkamapper]

What steps will reproduce the problem?

1. Open WMS "Norway orthophoto (more recent, more zoom)"
2. Edit for a while (normal size file)

Tile size was set to 1024

What is the expected result?

Normal editing

What happens instead?

CPU usage increases to very high level
"Out of memory" message (8192 MB available to JOSM)

Possibly related to #20443 and #20207

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

Revision:17428
Is-Local-Build:true
Build-Date:2020-12-30 15:56:02

Identification: JOSM/1.5 (17428 SVN en_GB) Mac OS X 10.15.7
OS Build number: Mac OS X 10.15.7 (19H2)
Memory Usage: 8192 MB / 8192 MB (4183 MB allocated, but free)
Java version: 15.0.1+9, Azul Systems, Inc., OpenJDK 64-Bit Server VM
Look and Feel: com.apple.laf.AquaLookAndFeel
Screen: Display 69733568 1440×900 (scaling 2.00×2.00)
Maximum Screen Size: 1440×900
Best cursor sizes: 16×16→16×16, 32×32→32×32
VM arguments: [--module-path=/Applications/JOSM.app/Contents/app/mods]
Dataset consistency test: No problems found

Plugins:
+ PicLayer (2a9aa7a)
+ apache-commons (35524)
+ apache-http (35589)
+ changeset-viewer (25)
+ conflation (0.6.6)
+ ejml (35458)
+ ext_tools (35640)
+ geotools (35458)
+ imagery-xml-bounds (35640)
+ jaxb (35543)
+ jna (35662)
+ jts (35458)
+ opendata (35640)
+ pdfimport (35640)
+ reverter (35688)
+ todo (30306)
+ utilsplugin2 (35691)

Tagging presets:
+ https://josm.openstreetmap.de/josmfile?page=Presets/LaneAttributes&zip=1
+ https://raw.githubusercontent.com/OpenNauticalChart/josm/master/INT-1-preset.xml

Map paint styles:
+ https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://raw.githubusercontent.com/OpenSeaMap/josm/master/CEVNI_MapCSS.mapcss
- https://raw.githubusercontent.com/OpenSeaMap/josm/master/INT1_Seamark.mapcss

Last errors/warnings:
- 02268.708 W: Not downloading all tiles because there is more than 18 tiles on an axis!
- 02268.861 W: Not downloading all tiles because there is more than 18 tiles on an axis!
- 02269.018 W: Not downloading all tiles because there is more than 18 tiles on an axis!
- 02269.181 W: Not downloading all tiles because there is more than 18 tiles on an axis!
- 02269.337 W: Not downloading all tiles because there is more than 18 tiles on an axis!
- 02269.486 W: Not downloading all tiles because there is more than 18 tiles on an axis!
- 02394.269 E: Failed to locate image 'https://www.kartverket.no/Content/Images/logo-graphic-512.png'
- 02409.297 W: java.net.SocketTimeoutException: Connect timed out
- 02409.298 W: Already here java.net.SocketTimeoutException: Connect timed out
- 02409.401 E: Failed to locate image 'http://openptmap.de/favicon_pt.png'