So when walking next to a block placed by me or a friend I can go straight through. This is only the case with my head. This only applies to some blocks and I don't know why. The blocks don't have to be placed by a player for them to be able to walked through. This can also happen in the overworld, not tried it in the end yet. It doesn't seem to happen with blocks that were placed some time ago, so maybe it happened with an update.