Internal extensions can't call external main number

This is an odd nuisance issue that I’m not sure how to go after. I’m using FreePBX 13.0.163 with a Sangoma A101DE card. We have a number of phone numbers. Some are DIDs mapped to specific extensions, and these work normally in all regards. The rest all are all covered by a catch-all inbound route. All but one of these work fine. The remaining one is our main number (e.g. the one we publish on brouchures, etc.). It works fine for outside callers. If, however, an internal user dials our main number, the call fails with “sig_pri.c: Span 1: Channel 0/1 got hangup request, cause 17”. The only reason to do this is testing (e.g. “can we receive inbound calls?”, “is the right message playing”). The internal users can call any of our other numbers (either DIDs or unassigned) without issue.

I don’t understand why FreePBX is treating this number differently. The only thing I can see that makes it special from FreePBX’s point of view is that it matches the CID for outbound calls, but I tried changing that with no effect.

I’ve compared log files of a call to the main number and a different unassigned number, and they match (with suitable time-stamp, process #, and phone number changes) until the sig_pri.c message above.

We tried this a few weeks ago and it worked. Since then perhaps 20 modules received updates. I also replaced the Sangoma A101DE card with the spare (to make sure the spare works), and ran setup-sangoma again. I’ve checked the new configuration files generated by setup-sangoma, but I answered all the questions the same and the resulting files appear to all match. The card shouldn’t know that number is special, as far as I can tell.

So, is this a FreePBX configuration issue, a Sangoma issue, or something else? It’s just a nuisance, so we’re not thrilled about taking more downtime to put the old card back in, though we’ll resort to that if we can’t solve this another way.

Can anybody suggest a reasonable path for narrowing this down?