Is it a mod compatibility issue?

Yes

Minecraft version

1.19.2

Describe the issue

forgive my "lazyness" in copy pasting most of the details from the other one as i wrote it first XD
when using the "First Person Model" mod with IP, portals with "non conformal" rotation (i.e that "change" the direction you are facing when entered) create an incorectly rotated character model visible in the protal.

in this example i used the immersive protal "rotate y 15" debug stick (found in the "misc" section of the creative menu) to rotate a nether portal 180 degrees. this occurs on both forge and fabric versions of the mod.

tr7zw/FirstPersonModel#355