I just uploaded three different versions of a map in parallel, that is:

• Clicking the upload button on three different browser tabs
  
• Uploading all the maps before moving on to the next step
  
• Entering defails for each map before finishing upload
  

The result was, that the last map I uploaded was posted three times, but with the title and information of the other maps. When I then went to upload map again, I was able to resume the upload of the other two maps, which would have resulted in

• 1x Map Version 1
  
• 1x Map Version 2
  
• 3x Map Version 3
  

I didn't think about leaving the duplicates up for debugging reason, but their IDs were 42377-42381, where 42377 - 42379 where the duplicates and 42380 & 42381 are the maps that I used the resume upload feature for.

Hope this helps.

Edit: Also, 42379 reports as corrupted now, when trying to download it. Trying to edit it results in an error: "Object reference not set to an instance of an object."