There are two Multi File Upload pop-ups visible.

Prereq.: Use slow network connection & big files.

Steps:

1. Go to Media / Images.
2. Click "Upload sub-items" button.
3. Drag and drop first file.
4. Drag and drop second file.
5. Cancel upload of first file.
6. Cancel upload of second file.
7. Close the "Multi-file upload" pop-up.

Actual: Another MFU pop-up is visible with uploading of one of the files.
Expected: There is one pop-up, both uploads are terminated when canceled.

Remarks: Related to this, if not canceled files are uploaded twice.