How to reproduce:

1. Summon a still wandering trader in 1.21.1.

   /summon wandering_trader ~ ~ ~ {NoAI:1b}

   In the following steps, be careful not to move your camera or your character.

2. Take a screenshot of the trader.
3. Close the world and open it up in the most recent 1.21.2 version.
4. Take another screenshot, this time in 1.21.2.
   → Note that the wandering trader is slightly smaller in the second screenshot.

I have attached a video of this bug in action—the pale oak is 1.21.2, while the spruce is 1.21.1.