Hey, not sure if your issue is related but if you are having errors switching to OFFBOARD_MODE it might be worth checking that you sent at least 100 commands before switching modes, or else you will have an error and the transition will not work.
I believe this is to protect against an absence of commands that would result in the motors stopping and the drone crashing, or something of the like.
Might be that, might not be ; but it is for sure a behavior that could surprise you. Hope it helps.