OK so I think I have a repro (need to confirm but this is the gist of it), it is a bit late on a Friday to think of a fix, but we can look next week.
Disable download remote images
Create a post with the body:
Register an account for bob.bob11
Enable download remote images
Rebake the post
What happens is this download triggers and edit, which in turn triggers a scan for mentions, then we figure out we never notified on the mention and go for it.
Its very very subtle and only affects a small number of posts… unfortunately for your import there are a lot of PMs with images and mentions that makes this problem particularly painful.
We need to fix it so the edit is flagged as “special” and bypasses some of the pipeline.
I think simplest workaround for now is just to untick the “download remote images” option and we can then do another rebake later when we fix the root issue.
Going to add this to @zogstrip’s list so he can have a look next week since he spend a fair amount of time in the edit pipeline.