So you are aware of this from our conversions I've been working to reproduce, got some help, did binary removals etc it seems to down to a combination of several mods

with Astral sorcery build#32 , forge 2782 and this modlist:
https://hastebin.com/acusucifex.nginx
(I could probably whittle this modlist down even further but I've already been at it for hours :P)

everything works fine.
The second you add in gamestages the bug returns. On first login your armor bar is unresponsive, negative potion effects dont show up. you can often instant break blocks. Relogging fixes the issues.
These errors are thrown in the logs:
https://hastebin.com/bavafaheca.rb

these errors do not exist without gamestages installed and the bugginess never presents over 10+ new games and relaunches