I've now found out that ESET Endpoint Antivirus, running on my Linux desktop system, seems to be the cause for two problems:
1) Deadlock when installing or updating Flaktpak containers:
When flatpak tries to download something, the data rate drops to a few bytes/s after a few seconds. After a few seconds more, I get a super high system system load with an almost frozen mouse cursor and an unusable desktop environment.
2) Veracrypt file containers can't be unmounted completely. After unmounting in the VC GUI, they disappear there but are still accessible on the command line or file managers.
When I run
systemctl stop eea.service
before, I don't have these issues. Are there any tips to solve this problem?