From my experience, Oathbound Chests and Heist Bags (the C4S4 one that has the chance to drop Rocket Rams) are bugged. The Oathbound Chests are unable to be searched, while the Heist Bags are always searched.
I was using a Level Sequence when bug testing my map and am unaware if this is a bug with the Sequencer itself or a bug with the chests themselves.