What browsers on what OS are you guys having issues on? I tested all the combination of multiple game engines (2 games for each engine I tested) and browsers and everything seems to work when im logged in or not without an issue.
Game engines I've tested:
Game Maker Studio HTML export
Browsers (tested on Windows 10/8.1 and Fedora):
Can you share a link to the archive you're trying to upload to GJ so I could reliably replicate the issue?