Freepbx server freezing server stays up but no calls internal or external

This is happening on and off on the same days of the week for a few months now.You can not make a internal or take external calls. When you check FreePBX it looks ok it shows that there are call in progress but when you check the phones no one is on a call . The only way to fix this is to restart the system. If we check the voip account with the voip provider it shows that the account is still up. RunningFreePBX
Any help would be greatly appreciated

Next time you notice a disruption, call your VOIP provider and see if they can tell you what they show from their side, i.e. your box sending some message back - or not. Who is the carrier and what is your trunk configuration?