Sometimes the player will phase into a one block tall area. Originally this only happened with leaves, but as of the latest hotfix, it now occurs with solid blocks. I first encountered this issue a few months ago when a player on Nintendo switch was walking through trees on my world. I checked my settings, and I had no behavior packs. I was playing around with this bug in my survival world, and I logged out and it stopped happening, so I could not take a screenshot. It does not always happen; maybe it is just a client side error