MSWin: "Error detected while processing function LanguageTool_lopen[1]..."

[harriott]

:!java -jar C:\LanguageTool\languagetool-commandline.jar -h works fine
(and in PowerShell I can java -jar C:\LanguageTool\languagetool-commandline.jar <TextFileToCheck>)

Very early in my vimrc, I have

let g:languagetool_jar='C:\LanguageTool\languagetool-commandline.jar'

but :LanguageToolCheck gets me:

Error detected while processing function LanguageTool_lopen[1]..languagetool#Check:
  line   43: Command [java -jar C:\LanguageTool\languagetool-commandline.jar -c utf-8 -d WHITESPACE_RULE,EN_QUOTES -l fr --api C:\Users\troin\AppData\Local\Temp\V992ED4.tmp 2> C:\Users\troin\AppData\Local\Temp\VA22ED5.tmp] failed with error: 1
  line   46: ['Exception in thread "main" java.lang.StackOverflowError', '^Iat java.util.stream.Streams$ConcatSpliterator.estimateSize(Unknown Source)', '^Iat java.util.stream.Streams$ConcatSpliterator.estimateSize(Unknown Source)', ...