Suggestions in spellchecking for userSpecificSpellerWords are stopped working after LanguageTool version upgrade

trying to update the LanguageTool version from 5.0 to the latest (6.4 for now) and facing with a lot of tests failing in our project with the next root-cause:

we actively using a custom words list for spellchecking. This list is sets via UserConfig(userSpecificSpellerWords) to JLanguageTool object in our implementation.

After checking the text in the 5.0 library version, suggested replacements always contains our specific words in case of a mistypo. For example: we have user specific word ‘textt’ and when we trying to type ‘texttt’, the suggestions contains ‘textt’, ‘texts’ etc.

After upgrading the lib to 6.4 version the behavior the next: when we have user specific word ‘textt’ and trying to type ‘texttt’, the suggestion list is NOT contains custom word ‘textt’, only the words from the lib dictionary. However, trying to type ‘textt’ is not invokes any spelling rule issue, so this word is takes part in the spellchecking.

Actually, I just have played with versions, and figure out that such behavior appears since 5.5 version.

Is it an issue or user specific words suggestion should be configured somehow?

Thanks in advance for an answer.