I am OP on my online fabric server v1.20.4. After going through the portal, two noticable problems appear; I think they have a similar cause related to player state on the server.
I use a portal with the strong enhancer rune, with both end in the overworld.

Problems:

• I can no longer access the game mode switcher (F3+F4).
• Easy Shulker Box mod no longer correctly shows the content of shulkers, ender chests, etc.

I'd appreciate any assistance. Feel free to contact me with any questions.

It also makes it seem like I have no xp after going through a portal from this mod. Once I gain some, I "regain" the xp that seemed gone.

Traveling to another dimension remedies the issue. Both vanilla portals and custom portals work for this purpose.