so it has done it again (it's sometimes been inconsistent) and I finally remembered to get a screenshot of it, and had time to reply here.
1. Windows 11 Pro Version 24H2 OS build 26100.4652
2. Start11 version 2.53, and I just double checked that it's the latest version (according to the checker in the app)
3. The line through the icons is very thin, but is most noticeable through explorer, and you can see the behavior of the start button.

On a side not I also tried using the default start button, and the line would still show up, but with the default start button it would line up with itself.
Please advise next steps, thanks!
--edited to add having time to reply here.