SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6): Invalid SQL: SELECT COUNT(articleid) FROM bb1_lexika WHERE visible = 1 AND catid = 2 AND INSTR('',UCASE(LEFT(topic,1)))>0
mysql error: Illegal mix of collations (utf8mb4_general_ci,COERCIBLE) and (latin1_swedish_ci,IMPLICIT) for operation 'instr'
mysql error number: 1267
mysql version: 5.7.22-log
php version: 5.4.45
Date: 22.10.2019 @ 20:43
Script: /lex.php?action=letterlist&catid=2&letter=%C4%D6%DC
Referer: