Call Fails - incoming and outgoing including internal

Over the last few weeks we have had a recurring issue with calls.

Inbound calls > sometimes users have to redial to get through. Just get a call failed.
Outbound calls > sometimes just a dead line or comes up call failed. but if you redial it works. (no response i believe my phone says)
This also affects things like call pickup.
This also affects internal calls.

We have made no modifications recently. only updated vitalpbx twice (v3)

any insights or what we can do to troubleshoot etc?

Thanks

Have you gotten in touch with your VoIP provider about it?

Have you tried analyzing the Call Logs or using SNGREP to get more information about this?

usually i would look at the voip provider, but this is happening with internal calls also, for instance internal calls and call pickups.
I am not sure where to start so im about to open a ticket
Thanks

I afraid thats you need to use prameter insecure=invite in sip profiles