Open editor, place a player unit directly in the water with a TRG-20
this addWeapon "arifle_TRG20_F"; in the init script of the unit
And you won't be able to move.
Now try it with
this addWeapon "arifle_SDAR_F"; and it works fine.
This appears to be a new bug as was not present in most versions up until recently.