Possible fix multiplayer descync: delete all your folders, including config foldr, reinstall game.

[Lord of Beer]

Uninstall the game.

Delete these folders:

C:\Users\username\Documents\Paradox Interactive\Hearts of Iron IV

C:\Program Files (x86)\Steam\steamapps\common\Hearts of Iron IV


It seemed to fix the problem for the players that were causing desyncs in our game. Perhaps some settings from 1.4.2 are sticking around and causing bugs for you.

 

[Ironside121]

Updating to the 1.5.1 Beta fixed my desync issues, thankfully. So anyone getting them on 1.5 should also try updating to the Beta.