With RandomPatches 1.18.2.1 and BetterPortals 0.3.5, crouching while looking through a Nether Portal causes the view to have a sort of delayed self-correction in position.
Shown here: https://imgur.com/bc5A5Fm
This issue is more visible with Five Feet Small installed alongside it, but does not require it to occur.
A more visible example using 5FS: https://imgur.com/jyUD0DC

Additionally, with RandomPatches installed, after going through a portal once, this effect breaks entirely, causing the portal to not self-correct. This affects all portals, even after returning to the original dimension. This has been observed both with and without Five Feet Small, but the example shown is using it for visibility: https://imgur.com/2c4HTKP

I originally mislabeled 5FS as Nimble in my earlier post, however I meant Five Feet Small.
It turns out 5FS is not actually part of the issue at all, it only makes the effects more easily visible due to the height difference.