Based on a response from support they indicated that posting here is something they monitor to determine the severity of an issue.

Like others have stated, attempting to watch a broadcast via any external browser is seeing the broadcast play for approximately 30 seconds and then it loops. The loop will even continue after the broadcast has technically ended.

I have tried watching broadcasts on multiple devices and so far the only place I can watch broadcasts live is using the Windows edition of the Steam client and watching via the built-in browser.

I also have Steam setup on a Linux install, and the built in browser for that isn't working for broadcasts at all. I've tried Chrome, FireFox, Edge, and numerous other browsers on PC and Android, with no luck

The Android Steam App where you can watch broadcasts as well is having the same looping problem.