PHP Errors

I have many of these in my server log:

20.06.2018 06:20:06 betatest.opajaap.nl [client 31.161.24.0] PHP Warning:  Parameter 2 to qtranxf_postsFilter() expected to be a reference, value given in /mnt/web20.../htdocs/opajaap/betatest/wp-includes/class-wp-hook.php on line 286

PHP version 7.2.5