This sounds very similar to a recent post about objects briefly appearing for a frame after scene transitions: シーン遷移後にオブジェクトが見えてしまう - Baz の #2
The likely cause is the same. The initial state takes a couple frames to run after loading, so what shows during that brief moment is whatever the object itself is set to in the scene, not what’s defined in the initial state. That would also explain the inconsistency across your objects. The ones that match their initial state closely don’t flicker, and the ones that differ do.
As a workaround, you can try matching the object’s base scene setup to what you want the initial loaded state to look like (visibility, animation frame, etc.), so there’s no visible mismatch during that load window.
That said, I think this is becoming an interesting pattern worth raising. Having to mirror the initial state on the object itself isn’t great, especially for save/load and scene transitions, where you’d expect the initial state to just apply instantly. I’m going to bring this up with the developers to see if the load behavior here can be improved.