2026-01-31 03:13:26 [4] VoIP: ASSERT: voip_findInCallEndpt:3697 sip < SIP_MAX

is an error from the system log.

I have two SIP connections, but from the log, I cannot see if one or both is causing the problem.

If the time stamp is correct, it is happening at three in the morning.
Telephony does not work after this, but a reboot fixes it. Obviously, this is not tolerable. You do not know you cannot be reached until some days later, you notice you have not had any calls.