While grinding experience on a spider XP farm, I took notice that eating steaks while standing on a double chest (one side has a hopper on top of it) lets me fall through the chest onto the block below. By the time of report it has happened two times. Exact conditions: Light Level 0, Chest surrounded by solid blocks, a trapdoor on top of the hopper (on an adjacent block)

(Update)

After reloading the world by standard means while standing on a chest (even singular), while the lower hitbox is surrounded by solid blocks I discovered that I fell through just by rejoining. If reloading on a chest standing clear of the blocks aside from a wall, teleporting the player on the floor. A quick test in creative mode has not shown any signs of a bug.

(Update)

Attempts to recreate the bug in a new survival world or on surface are unsuccessful. Continues to happen inside the grind room. Hypothesis: 1)This has to do with 1.20.0 to 1.20.1 transition (Unlikely), 2) This has to do with a spawner(Likely, as it happens anywhere in the room), 3) This has to do with continuous jumping on the chest, 4) This has to do with a previous creeper explosion in the area of the bug(Most likely). It could be a combination of those, as alone by themselves they do not always align with the results