Good afternoon. There are several FreePBX stations in the network, the trunks are configured, everything works, but from time to time you cannot call one of the stations (error: all lines are busy) or make a call from it. Rebooting solves the problem for a few days. Where to look for a problem tell me ??
The logs - without them it is all guesswork.
The router - my guess is that a NAT or firewall rules is timing out and not getting re-instated.
You can also try to change the transport from UDP to TCP, that solves many problems sometimes.