Some German translations are shown even if language is set to English

[GerdP]

What steps will reproduce the problem?

1. Make sure JOSM is started without language parameter and language is set to en (English)
2. Press F12 to Open preferences, select validator tab "Tag checker rules"

What is the expected result?

All texts are in english

What happens instead?

The mapcss tests are shown with German names, e.g. "Unnötige Merkmale"

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

I use a Windows system that is configured to German language and sometimes use German.
The German texts also show in other dialog elements like popups or tooltips.
Can reproduce this with tesed and latest.

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2021-09-03 03:12:33 +0200 (Fri, 03 Sep 2021)
Build-Date:2021-09-03 01:31:19
Revision:18193
Relative:URL: ^/trunk

Identification: JOSM/1.5 (18193 en) Windows 10 64-Bit
OS Build number: Windows 10 Home 2009 (19043)
Memory Usage: 528 MB / 3641 MB (314 MB allocated, but free)
Java version: 1.8.0_221-b11, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920×1080 (scaling 1.00×1.00)
Maximum Screen Size: 1920×1080
Best cursor sizes: 16×16→32×32, 32×32→32×32
System property file.encoding: Cp1252
System property sun.jnu.encoding: Cp1252
Locale info: en_DE
Numbers with default locale: 1234567890 -> 1234567890
Dataset consistency test: No problems found

Plugins:
+ apache-commons (35524)
+ buildings_tools (35823)
+ contourmerge (v0.1.8)
+ ejml (35458)
+ geotools (35458)
+ imagery-xml-bounds (35723)
+ jaxb (35543)
+ jts (35458)
+ o5m (35640)
+ opendata (35803)
+ pbf (35720)
+ poly (35640)
+ reltoolbox (35640)
+ reverter (35732)
+ undelete (35640)
+ utilsplugin2 (35792)

Validator rules:
+ c:\josm\core\resources\data\validator\geometry.mapcss
+ d:\java_tools\JOSM\mygeometry.mapcss