AMO Submit a new version page hangs on validation step

This is a repeat of a problem I saw earlier this year, maybe in April. At that time, several other developers reported the same thing as I experienced. It’s happening again.

After clicking the [Select a file] button on the page, the validation progress meter fills from 0 to 100%, “100% complete · 2.11 MB of 2.11 MB”. However, the [Continue] button is not enabled and the animated progress meter continues to shimmer.

In other words, the process hangs at or near the end of the validation process.

Nothing significant has changed in my extension source code and I am pretty sure this issue is unrelated to the specifics of my extension.

I’ve tried to upload the file twice: I refreshed the page and then clicked the [Select a file] button to retry. Same result.

I am using the up-to-date version of Firefox.

Is this a known issue right now? If not, can I report the issue somewhere?

Any other advice or recommendations?