I do not believe that we have enough information here to find the problem. The output that you posted indicates that there is a virtual-access interface interacting with a dialer profile. At 13:16:27.649 the virtual-access is bound to the dialer profile and at 13:16:27.925 it is unbound. It would appear that during the elapsed time that the dialer profile attempted to do something, but we do not know what it was attempting and what the outcome was.
Perhaps we would get more useful information if you run and post the output of debug isdn q931 and perhaps the output of debug dialer.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...