I think pehkui is the issue because when I removed it it worked as expected. This Also Happend in Single player. I have a small hunch that this could be due to some of the bigger mods such as Create ...

In Minecraft, all entities and the player's characters have a specific movement speed and size. Some mobs are massive in size, while others are incredibly tiny. Since the game is over a decade old, ...

[Bug] With Pehkui and Immersive portal installed, my size doesn't change when going through a portal (forge version) Virtuoel/Pehkui#159 ...