"Last updated" sort option on group details page is inaccurate or not as expected

Description of the problem

We have several private repositories for our group, but even of the group's public ones on gitlab.com, the sorting for "Last updated" appears to be inaccurate or it defies expectations.

We expect that the "Last updated" sort option will sort any repository that's had some sort of update made to trigger it's last_activity_at properties as indicated from this older issue from the gitlab-foss issues list. There, @markglenfletcher indicated that several activities would trigger this change on a project. In my opinion the most important activities are pushes to the repo, merge requests, and issues—obviously the many other activities listed in that thread are also important.

This is our public group's "Last updated" (sort=updated_desc) sort:

This is one of the projects that had both a recent push and merge request:

Comparing the above two screenshots, you will see that the "base-modules" project had both a push and merge request as recent as 3 days ago, yet it appears in the sort with the inaccurate activity of 9 months ago.

Even if we look at the issues list, assuming only "GitLab UI" activity was the case, there are issues created 8 months ago versus the 9 months displayed by the group's detail page:

Something is rotten in the state of GitLab.

Which Group/Project (with full path) is experiencing the issue?

https://gitlab.com/barrel?sort=updated_desc

Approximate date/time when the error occurred.

It's been apparent for some time now, but I'm just now getting around to reporting it. Some inconsistencies related to this can be seen:

Describe what you were doing right before the issue occurred.

N/A. As mentioned, we've observed this issue for some time and was hoping it would get fixed via other tickets reported above. Perhaps those were different issues, but we've provided screenshots above to support our claim.