can trigger it pretty reliably trying to repeatedly fly under a block, (1 block gap) after some testing it seems the game thinks your stuck in a 1 block height. Can walk through blocks at head height but not on ground level. Seem fun for the most part, except if tour in the glitch hunting shulkers, they will float you into the ceiling and since your head glitches through and not your feet you begin to suffocate. Can get out of the glitch mode by just jumping and deploying elytra a few times.

VIDEO: https://youtu.be/Hmm41kIigU8