Merge requests are not updated when new commits are pushed

Sometimes newly pushed commits are not visible on the commits tab on a project/merge_requests/123. The commits are showing on the commits tab on project/commits/branch-name. When the MR is closed and opened again, the new commits become visible are showing up on project/merge_requests/123.

This was filed before as #368 (closed) which is closed already, but this happened again with 8.8.5 (we updated to 8.9.0 this morning).