Excellent postback, and good job.
Note that those rtp entries may appear unrelated, but often the nat mapping closing prematurely is what kills the network pathway for the registered sip account to send a call. Once the nat mapped network port closes, a call to that (still registered) account may fail due to the missing network port. So it was a related/valid concern (for the record) just turned out to be not the problem for your situation.
In any event, your post was quite clear and will likely help others in the future! Well done.