Is it a mod compatibility issue?

Yes

If it's a mod compatibility issue, please provide the link(s) to the incompatible mod(s)

https://modrinth.com/mod/worldedit-cui

Minecraft version

1.20.4

Describe the issue

This issue only occurs with a portal in view

if the portal is a normal portal (e.g. a 1x1 portal into a 1x1 portal) the bounding box will just vanish at some angles
if the portal is tilted forward or backwards, then it will just vanish at some angles.
if the portal is tilted any other way (left/right or side-to-side), the bounding box will just show in random places in the world at random angles.