Some information
Note that this only occurs on occasion, and it relates to MC-194173.
The bug
Entity hitboxes (including the player's) occasionally shift upwards or sideways while picking up an item or an experience orb while facing to the north. I discorvered this while testing MC-194173, and I found this with endermen (but it likely occurs with other entities as well, but I haven't tested it). It usually only occurs with one (if any) entity within view, as you can see in the attached video.
How to reproduce:
Look to the north, facing some entities (the more entities, the more you are likely to see the bug)
Enable hitboxes
Drop an item in front of you (or an experience orb)
Pick the item or experience orb up
Notice that on occasion, entity hitboxes shift upwards (but not the entity itself) for a few frames.
Related issues
Attachments
Comments


Only happens with fast/fancy graphics.
Edit: I've changed the screen recording so that it can be played without being downloaded.
Edit 2: I've added a video that shows the player's hitbox shifting, from MC-194197.