Hello and welcome @LordSimal 
I think your report is more similar to this Contribute > Bug so I’ve slipped your post across. 
We think it’s connected to the ‘typing too fast’ flags not being retained in the Review Queue history, and when following the individual notification from the menu you land on a specific page for that flag. When deleted, the page no longer exists which then throws up that info box.
Someone has been assigned to investigate, and I think a fix is in the pipeline. 