Hello,
I noticed a weird portal behavior, I explain it with pictures.

First portal, that I created:

Portal in the dimension:

?New? portal, if I go back to the overworld:

This new portal work fine, if I go through this in the dimension and back, but I can't come back to the old portal.
(destroying the new portal always create a new one some blocks away)

MC: 1.12.2
Cavern: 2.3.0
Forge: ...2854
It's on a Server.