Popping sensation within center of upper shaft?

Hello all, been a lurker here for a little while and have been absorbing plenty of information on PE, as well as practicing.

A little about my routine:

I have been been practicing PE for about 5 months now mainly doing manual static stretches an hour twice daily for 5 days, with 2 days of manual clamping embedded with in those 5 days, and 2 rest days with no PE. I have been seeing some nice results.

Anyway my question / concern is about this strange popping / bubble sensation I have felt in my penis in the middle in the upper shaft near the glands twice during a manual clamping session.

Its hard to say where the sensation was exactly located ( maybe the urethra ) Best way I could describe it as a bubble forming then bursting very quickly, definitely a startling sensation that made me stop what I was doing all though there was no pain and no negative side effects following the incident. Both times this has happened I was 100% erect with my hands in the clamped position on my penis and very stimulated.

I have read about lig pop’s but from what I understand those mainly occur when stretching not clamping and often felt at the base, not in the middle towards the glans.

I am just wondering if anyone out there has experienced this sensation, or have read about, is it dangerous etc!

Would be awesome to hear if anyone has any info on this sensation, since I have not been able to find any similar stories !

Thanks again.