MySQL error in file: /engine/modules/show.full.php at line 981

Error Number: 3685

The Error returned was:
Illegal argument to a regular expression.

SQL query:

SELECT /*related_ids_2*/ id, date, short_story, xfields, title, category, alt_name FROM dle_post WHERE category regexp '[[:<:]](20110|12|2022|2023|2024|2025|20021|20034)[[:>:]]' AND MATCH (title, short_story, full_story, xfields) AGAINST ('Тайны финской войны ') AND id != 80684 AND approve=1 LIMIT 12