Issues with trying to make a cutscene model

So for about 2 years now I’ve been looking for a way to animate cinematic cutscenes efficiently and I think I found a solution. I basically put all the models into a large rig with a hierarchy that I can use to animated them and play the animation in engine. The only problem is that for some reason the rigs will copy each others animation somehow despite being two separate instances.

I ran some tests and concluded that for some strange reason this problem only appears to happen with r15 rigs and nothing else.

Below are two animations ive made trying to find a solution. the one with the red and green blocks are working normally. The “rig” on the left is moving fine while the rig"\ on the right is staying still, not copying the rig on the left. But in the video with the R15 block rigs, the rig on the left is doing movements that shouldn’t even be possible. His torso is moving upwards even though I only animated that happening on the rig on the right. I just want some answers/theories as to what could be happening here. I’m so lost and confused at the moment.

here’s what the hierarchy looks like

Central Part (Primary Part)
Character Part
Rig 1
Any Limbs / Objects in Rig 1
Rig 2
Any Limbs / Objects in Rig 1

Normal rigs

Weird rigs