I took the example that "Grimmy" posted on page 2
And I can confirm that it fails with (Worker On or Off) but it took a lot of tries to start failing at first and it was more random instead of waiting the 30secs as the instruction mentioned.
Example:
My failings fail after just wait 1 sec or 2 or doesn't matter how many I just keep travelling from one layout to the other until it fails, some times takes more than 50 tries back and forwards but it will fail 100% on all the attempts, at least for me I manage to reproduce it like 8 times.
Another note is that when it fails it will fail forever even if you change the layout and come back it will still fail every time, so it will reset only if you hit preview again.
I hope they can fix this issue as urgent as possible as a lot of users heavily use Ajax like me or it will brake many Games.
Error that C3 prints on preview:
Console Error:
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Video Worker mode On:
https://www.dropbox.com/s/0s5jym4zi2zeqj1/ajax%20fails1.mp4?dl=0
Video Worker Mode Off:
https://www.dropbox.com/s/xz8tsplr62nsmdr/ajax%20fails2.mp4?dl=0