Simple enough, got a Titan with Stronghold build and was plying around at clearing rooms just reflecting shot back at everything.
After a while, on the 3rd wave of 4 for that part of the mission it punted me to orbit.
Guessing waving the light saber around does not count as activity.
That's a bug, I had a nice spot covering the whole room ... .
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You need to physically move your character or interact with menus to avoid AFK detection. It's been that way for years.