Thanks for the fast reply. It seems that you are right - there is an out "of memory-error".
[81472.533565] oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),cpuset=/,mems_allowed=0,global_oom,task_memcg=/system.slice/clamav-daemon.service,task=clamd,pid=15850,uid=109
[81472.533583] Out of...