Here we have TNT handing back to Cartoon Network sometime in 1998. This does actually contain a fault in which the “bouncing blocks” ident fails to play complete with a double DOG
in the top right, then into a Toon Byte which if I remember and I could be wrong they used these as fillers when faults occurred or they had time to fill if programmes ended early.
Sadly it seems the videos are long gone from Youtube but Turner Broadcasting UK had a pretty major breakdown for most of the day on 27 July 2006. From what little info remains, apparently their channel transmitters were in Soho and there was a huge power cut due to high heat levels so the channels couldn't run properly and had to run off some sort of backup that was about a year or two old. But it couldn't show commecials and for most of the day had a scrolling banner saying the channels were suffering massive faults
It was notable as Boomerang actually showed classic cartoons on it's backup, and the UK Toonami showed it's old anime-style lineup instead of the newer live action angle it had at the time.
I asked around on the lostmediawiki forums about this, though I haven't got a reply yet. They've had some luck finding missing breakdowns and technical issues footage (most recently finding some Viacom Australia footage when they had a technical breakdown a few years ago)