@vadim OK, so, the root cause is the DNS resolution issue . Looks like it starts to fail at some point. Is there something in the network that blocks DNS requests?
Looks like this is some internal network? Maybe try to set up a forward zone to the internal DNS (https://docs.cloudron.io/networking/#internal-dns-server) ? In the next release, we are moving away from unbound since it's causing not-so-easily debuggable situations (like this one).