LanguageTool can't handle large documents

The LanguageTool extension can’t handle large documents! I have a 400+ page document that has no red, blue, or green LT squiggles on it anywhere, and I can’t seem to get it to work. I have gotten it to work on shorter documents, and if I open them right now in their current state, the squiggles appear there. I tried removing the cache folder from the app data to see if that might help (it didn’t); I also set it to “Text Check” rather than “Paragraph Check” mode because I read somewhere that that might help (it didn’t!). I also have it set to use multiple cores since this is apparently a fairly labor-intensive process. No dice.

I did at one point get a javascript error message, which I can’t reproduce at the moment, but if it reappears, I’ll edit this post to include a screenshot.

I realize that LanguageTool is no longer supported, but when I tried its successor, WritingTool, I had some difficulties with it, and so I “downgraded” to LT (EDIT: version 6.4). It looks like WritingTool has been updated since I last tried it, so maybe switching back to that might work . . .

Anyway, that’s the state of play, any suggestions on how I might be able to get LT to work would be much appreciated!

EDIT: I’ve also noticed that LT isn’t checking words in a certain font, in this case “Courier Prime,” which is installed on my system (Using Linux Mint 22.1, btw). I set Courier Prime as the default font in LO options, and embedded the font in the document, but no luck. When I cut and “pasted special>unformatted text” some sample Courier text into another document with a different font, the squiggles returned! What gives?

You don’t explain how that relates to

This tells nothing decisive about LT working state - you may be correct (if the “squiggles” are created by other modules, like spellchecker or Lightproof built-in module); or you may be wrong, and the squiggles are created by LT, meaning it does work - but that needs explaining, e.g., checking how the context menus look like for those squiggles. Or what specifically do you put into “can’t handle”? What is your expectation, and why?

Fonts don’t matter, but the language of text does.