If there is a moving block placed next to another block (for simplicity's sake, just let's assume this is a normal block) and the block moves up/down from the player's current view, the ball can roll on this moving block at any time, no matter if it is lower, higher or at the same level as the ball. The ball rolls on the moving block as if it were a neighboring block.
I bet this bug manifests itself in some other similar behaviours. It could be that for other axes the moving block is buggy, too. But I did not test this.
I have attached an example level. The moving block just moves up and down (from the starting view). It shows exactly the situation described above. Just roll forwards.