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://github.com/Qendolin/better-clouds

Minecraft version

1.20.1

Describe the issue

https://github.com/Qendolin/better-clouds

Causes major visual glitches when 2 or more portals/mirrors are in view together most notibly appearing to "flip" the camera

It looks compatible now..? I haven't encountered any issue yet, I will post here again if I find anything

It happens when 2 portals can both view the overworld at the same time.

otherwise portals/mirrors work fine (other than clouds not being visible through them)

dual mirrors also work but only in the nether/end and as long as it can't reflect the overworld through a portal