I have an ultra 4660x and still having the issue. Only with WeTV channel thus far.
If it's only one specific channel causing a problem, then odds are the channel is the problem. Sometimes they get corrupted during an update, and the best way to clear it is to uninstall the channel, reboot the Roku, then reinstall the channel. The reboot is absolutely mandatory, or the uninstall isn't complete. I have a 4640 and a 4670 Ultra, and both play long duration videos on YouTube and Prime without issue.
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