Seems likethere might be an issue with the device itself. I've been using my Chromecast on a shared hospital room connection for weeks and it's been suberb.
Thus is the answer. Some revisions of Chromecast have a slow CPU, and poor thermals so the CPU throttles even slower.
That normally isn't an issue, because all the video decoding is done in hardware, but enqueueing the video data chunks to be played is done by software. If the software is delayed because the CPU is very slow and the same event loop is processing loads of other crap (which it is), the video can glitch every few minutes.
The solution is for Google to do less crap on the main thread, increase the hardware video buffer size, or to get a faster CPU or have a better heatsink. The reason some videos do it while others don't is because the chunking is different sizes for different videos.
The problem is worst on the original v1 Chromecast. The latest software update reduced the clock speed because some devices were overheating and kernel panicking. You can still make the problem almost vanish if you do water cooling or take the case off and fit a fan.
