Can be lots of things going wrong, bad internet connection, temporary server issues, over sensitive anti virus settings or other security settings, bad router if you use any, old browser, etc.
I had troubles in past having a bad network router so that's one of meany possibility's.
Try systematically troubleshoot to find the origin of the issue.
Possible actions to take are;
- Refresh/flush browser settings (delete cookies/history, etc.),
- Update browser software
- Reset modem/router and reconnect
- If router is in your network try connect directly to your computer
- Try disable antivirus for time during upload and see if that helped, if it helped then check settings on anti virus, maybe some security exception need to be added
Do all these things step by step in order to try and zoom in on the possible issue.
It could be non of these but it does not hurt to try.
