So I ran into this super weird issue where Unity resets an UI elements Y-axis position when I anchor it either to the top or bottom of the canvas. This happens with every restart.
So for example, if I create a new image within the canvas at 30, 25 and anchor it to the bottom center, then after I restart the editor the image is moved to 30, 0.
EDIT: so I just tested this with a brand new project and I found the same behavior. Tested it again with another project I created a few months ago and could not reproduce it there. My current theory is that this is related to the editor version as the older project runs 2021.3.16f1 and the newer one runs 2022.3.3f1.
I moved the new test project to the older version and the issue was no longer present, this leads me to believe that this is a version dependent bug. Also tried the slightly newer version of 2022.3.4f1 and this version also had the described bug.
EDIT2: the issue seems to be fixed in 2023.1.3f1. Can I savely upgrade my existing project to this version? I assume upgrading is less of a problem than downgrading to 2021.3.16f1.