Database stored items like Issues, Merge Requests or Pipelines sometimes don't get imported as part of a Project Import

Through doing Project Imports on our test reference architecture environments we've noticed recently that sometimes, while the import repost as successful, that the resulting project has none of the expected Merge Requests. Even weirder we're not able to find any relevant errors as to why this is happening after examining the logs.

Some notes on this situation:

• Retrying the Import was fine and MRs appears
• Issues correctly imported each time
• Examining the database when the issue specifically happens shows a clean MR table with nothing in it.
• Issue has been seen by us in Quality 3 times over the last week or so on the latest Nightly Omnibus packages on two environments, one multi-node and the other single-node.
• Project imported - https://gitlab.com/gitlab-org/quality/performance-data/-/blob/master/projects_export/gitlabhq_export_13.0.0.tar.gz

Unfortunately at this time we don't have much more info to share but thought it best to raise for investigation since it could have a notable impact. We do have a dump of all logs from the single node environment that can be made available on request (issue happened on it yesterday).