Strange behavior when using MATCH

There is a strange issue with our index. Please look at the screenshots:

The field description is man_info_company string attribute indexed. Also, there are many other fields in the index. Index settings are the following ones:

morphology='stem_enru'
rt_mem_limit='1024M'
index_exact_words='1'
expand_keywords='1'
min_infix_len='3'
charset_table='0..9, english, russian, _, U+0401->U+0435, U+0451->U+0435'

The problem is that the query from the third screenshot does not return any documents. This is how the problem reproduced on our side:

  1. We execute a bulk insert query. Then we check the problematic SQL-query. It works well:

  1. After this we execute about 150 bulk insert queries and execute the problematic query one more time. It returns no documents as result (same as on the third screenshot)

Server version: 3.5.5 3f6a9fbb@210119 release git branch HEAD (no branch)

Please advise.

The related github issue is https://github.com/manticoresoftware/manticoresearch/issues/506