Unable to do lucene regex query ending with backslash


It seems I am unable to combine queries if one of them ends with a backslash.
This lucene query fails:

field:(/a\\/ OR /b/)

But these are just fine:

field:(/a/ OR /b/)
field:(/b/ OR /a\\/)

Same with AND

parse_exception: Cannot parse 'process.working_directory:(/a\\/ OR /b/)': Lexical error at line 1, column 41. Encountered: <EOF> after prefix "/)" (in lexical state 2)

We're on 8.13.2