zc 1.5.7c
Server version: 10.3.29-MariaDB - MariaDB Server
Database client version: libmysql - 5.6.43
PHP extension: mysqliDocumentation curlDocumentation mbstringDocumentation
PHP version: 7.3.28

If you use a to be depreciated feature in your sql. you are returned a blank screen as if the sql has failed. In the logs you get
[19-May-2021 07:15:15 UTC] PHP Recoverable fatal error: Object of class queryFactoryResult could not be converted to string in /ILSadmin/sqlpatch.php on line 753
A simple test i used SELECT @mark:=1;

If you put it into phpmyadmin you get the warning
Warning: #1287 Setting user variables within expressions is deprecated and will be removed in a future release. Consider alternatives: 'SET variable=expression, ...', or 'SELECT expression(s) INTO variables(s)'.
Don't know if it is a bug but thought I would mention it as I have fallen foul of it in my code.