I was messing around on one of the servers I play on and I was jumping on my chests, and I found that when I jumped on my top chest that had only two blocks of air above it, my head clipped into the block above, in a way that didn't stop my jump early, and my screen changed to show only the texture of the cobblestone I jumped into. I tried to replicate it again, and it seemed to only happen after I activated my elytra while jumping off the chest. I was able to reproduce the effect easiest by repeatedly pressing the space bar to activate the elytra as often as I could.