Guidelime appears to be causing issues with the quest log when grouped.

Here is a view of my quest log with no addons loaded.

Here is the same view, with just Guidelime loaded

You can see the numbers are squished. The numbers obviously indicate that the person I am grouped with is on the same q. If there were more than one I assume the overwrite would be larger.

I am using Guidelime-v3.038.zip

Thanks

Ty for reporting this issue.
It is (almost) fixed now as the titles in the quest log now will only be touched if there is an actual change by the addon which only happens when quest levels and/or quest ids are to be displayed.