Your updated workaround of reloading the interface does not work either. In fact it's made the situation worse because doing it has wiped all of the abilities off my quickbars

It’s the submersible droid under water, not the cargo loader droid that’s the problem. Going to stronghold and back does not get around this, as advised above.

After you get past the bug that locks you out of the room and you finally take control of the submersible droid - it doesn't do anything! You can't make it move and it won't take any input whatsoever. All player abilities are disabled, you can't use your fleet pass etc. You cannot progress the story at all past this point, all you can do is travel to your stronghold to get out of the lock. Relaunched the mission and you get the same problem. The game is unable to be progressed past this point. Imperial story playing as a Sith Juggernaut. This release has been an embarrassment.