While playing in ruins of vaux I spawned in my Tiger E at round start, started moving towards the objective and got the message Complete Your Objectives Soldier, killed their m10 and stuart before swapping to HE rounds and taking out infantry when it disconnected me for inactivity. This led to me losing a 50% xp booster from the battlepass rewards.
It often happens while using vehicles. The apparent reason is that the inactivity counter is not halted by mouse inputs only, so if you stand still on a spot without moving for too long, always in gunners view, you can be kicked despite being on a killing spree.
Best practical way to prevent this is to avoid the aforementioned behaviour. Even if you’re successfully camping, tap WASD and/or switch to commander view from time to time.
here’s the thing though, it was warning me while I was in the middle of actively moving.