assuming those are meshes my guess is that there’s small physics errors over time. what you could do is set their “CollisionFidelity” to box. and if that doesn’t fix it, maybe “PreciseConvexsomethingsomething.”
They are all unions. But. There is an invisible part box Thas the real physics go to. Unions cannot interact with them selves or anything other then the player.
If this is Jenga, you can try welding the blocks together until they are moved. Once a block is moved, that block and all blocks it was touching, unweld from the rest.
I found the issue, which was because of the green stars you see inside. They somehow gave all the blocks are really miniscule force something like .00019. in all directions. But this adding with all other blocks soon caused the parts to topple. Disabling the green stars fixes this. Ill make a seperate thread for the fixing the green stars.