Sounds like the device needs a hard reset and relink/reinstall channels, and also a forced update.
Bigger more complex apps sometimes break or have their saved data get corrupted and won't start anymore until a reset (and install fewer channels on low end devices).
Others have reported similar issues with YT now and again.
I had a "channel crashes device" issue with BBC iPlayer app on older express a while back, fixed with hard reset, update, reinstall.
Not a Roku employee