This sounds like a new one, great find!
Do you know if it is just the rendering output that disappears/freezes for some reason, and the content would actually be continuing to run on the background? I wonder if for example after setting sg.AntiAliasingQuality = 1, is it still possible to set sg.AntiAliasingQuality = 2 in the console by writing blind on the console. Does the CPU usage of the browser drop to 0% after the hang, or does it look like it’s still rendering/processing an event loop on the background in full steam?
Try doing a Development build, and after the page hangs, open the web page console, and type
document.getElementById('logwindow').style.display = 'block';
to show game’s console window (there will be a button in the future to toggle the log window). That might have an assertion failure message that was not otherwise shown.