S3 direct upload: Importing the same file at the same time fails

Reproduction steps: 

1) enable s3 direct upload 

2) go to WebUI

3) select any workspace

4) click on + to Add Content

5) Select "Import" and attach .mp4 file to initiate the upload.

6) open a new browser window and repeat steps 3-5 using the same .mp4 file while the first file is still uploading (use 25 MB + file so you have enough time to initiate the second upload)

Problem: the second upload fails.