@lgaetz and @PitzKey, well, it started doing it again after I upgraded DPMA…!
Call trace here
and
Call trace here post ‘reset’
Again, setting the ring group destination to a queue has fixed the issue, and again, setting the exact same setting back to its original setting causes the issue to disappear.
I’m glad it’s rare I do a DPMA update (or restart Asterisk, do a Yum update) because it is clearly a process that has gremlins…