I know it’s a couple of years late but I have the exact same issue with Premiere and the AVX system. So frustrating how it goes back to its reverted form after you manually sync it. It’d be the perfect wireless mic system if we could just properly sync it in premiere (or they could allow you to disable the encryption in the system).
I made a feature request on these forums that would be great if you could upvote so the Adobe guys can see it!
https://adobe-video.uservoice.com/forums/911233-premiere-pro/suggestions/40279495-audio-video-subframe-sync-bug