I was testing the glitches with shaders and this mod combined, and decided to relog while sprinting through a portal. When I logged back in I got jumpscared by a flashing copy of me teleporting up & down. Installed mods were this, the latest fabric api, and Optifabric. Breaking the portal did not fix the issue and neither did reloading the world again. Here is a screenshot of the glitch.

I will update if the glitch can occur without other mods.

Fixed. It will be in the next version.

I was able to reproduce the glitch without other mods, here is another screenshot and the log.

latest.log
It seems to be teleporting me right before I log out, and again when I log in. This could be related to the glitch.