Crashes when having multiple languages

MAC OS:

I am writing in Lithuanian most of the time; however, sometimes I write in English, and when I open a Lithuanian file, Harper is overwhelmed as it thinks that there are so many mistakes in the file, on every word, and crashes.

Grammarly does not have this issue; it understands when I write in English and when not, and when to check.

Is this somewhere in the pipeline?

This is the main deal-breaker for me now...

Thanks

No files, tests, or entry points are named. First reproduce the crash with a Lithuanian file while English is also used, then trace the language-checking path and add a regression test; done means mixed-language files no longer overwhelm Harper or crash on macOS.

Written by the indexing model from the issue text.