When one is standing inside scaffolding and tries to move forward to a adjacent block that is 1 level higher, the game tries to auto-jump as expected. However, the resulting jump fails to gain enough height to actually get on top of the block.

It doesn't matter how high the tower is; one scaffolding is enough. It does however matter if you started walking from inside the scaffolding (failing) or you're walking through (unaffected).