Random infinite loading on Bulk Import in Web UI

Steps to reproduce:

• Navigate to a folder
• Click Create button, then Import
• Drag and drop several different files at once to the dropzone
  => Import is ok, loading stopped, Create button available
• Start editing metadata
• Click Cancel
• Click Create button, then Import
• Drag and drop several different files at once to the dropzone
  => Import is ok, loading stopped, Create button available
• Start editing metadata
• Click Cancel
• Click Create button, then Import
• Drag and drop several different files at once to the dropzone
  => Import unfinished, still loading after 10 minutes, Create button disabled (labeled "UPLOADING")

A similar issue was fixed for 9.3 in NXP-23506. It seemed fine during first tests but the problem appeared during 3rd or 4th attempt to Bulk Import documents.