RRR,
[1] The newer hi flow [ Chinese ] stats can jam. They have a rubber seal/ring inside the main cup that is probably a little stuff. Dribble some ATF over the seal area it & then try it again in boiling water, it should work.
[2] As you found out, DCR & compression tests do not give a reliable indicator of an engine's tolerance to detonation. I alluded to this in my earlier post, which YR scoffed at, showing he doesn't know what he is talking about. There are PLENTY of examples of engines that, according to 'theory' should be detonating, but are not; & plenty of engines that are detonating [ like yours ] that should not be.
[3] I would richen the power cct of your carb, slightly. This should provide cooler combustion & may get you over the hump...
