Freeze on score upload when matching score to composition

This has been happening for about a week now.

To repro
1. upload score from Windows program for first time
2. Is this your original work? ->No
3. type into the field "Enter the music that your score is related to" - if you type one character more then there exists a match for in the Musescore database then the upload window freezes. The upload progress indicator also stops. Backspace does not release the window.

I've left it for up to fifteen minutes and not seen the window unfreeze. The "Cancel" option has no effect,but you can close the window and return to desktop Musescore.

If you go to https://musescore.com/my-scores the score can be seen to be uploaded successfully as a private score, not matched to the database.

If you re-attempt the upload then it may sometimes give you the normal upload window, but more often than not the window displays blank.

Workaround: upload the score as private, and match the piece from the web interface.