The package update somehow seems to have messed up the posix permissions on the grommunio-sync log folder and it's contents. After running a chmod g+rwx on it and the same minus -x on the two log files, I can now see what error grommunio sync throws:
31/08/2022 10:32:36 [ 852] [DEBUG] [budy@stephanbudach.de] -------- Start
31/08/2022 10:32:36 [ 852] [DEBUG] [budy@stephanbudach.de] cmd='Ping' devType='iPhone' devId='XXXXXXXXXXXXXXXXX' getUser='budy@stephanbudach.de' from='10.10.0.170' version='1.1.4-0' method='POST'
31/08/2022 10:32:36 [ 852] [DEBUG] [budy@stephanbudach.de] Used timezone 'Europe/Vienna'
31/08/2022 10:32:36 [ 852] [FATAL] [budy@stephanbudach.de] Fatal error: /usr/share/grommunio-sync/lib/grommunio/grommunio.php:1971 - syntax error, unexpected ';', expecting ')' (4)
31/08/2022 10:33:41 [ 851] [DEBUG] [billy@stephanbudach.de] -------- Start
31/08/2022 10:33:41 [ 851] [DEBUG] [billy@stephanbudach.de] cmd='Ping' devType='iPhone' devId='XXXXXXXXXXXXXXX' getUser='billy@stephanbudach.de' from='10.10.0.154' version='1.1.4-0' method='POST'
31/08/2022 10:33:41 [ 851] [DEBUG] [billy@stephanbudach.de] Used timezone 'Europe/Vienna'
31/08/2022 10:33:41 [ 851] [FATAL] [billy@stephanbudach.de] Fatal error: /usr/share/grommunio-sync/lib/grommunio/grommunio.php:1971 - syntax