Thanks for reporting the bug. Unfortunately, I don't have a Windows 7 machine for testing and can only try these links on Windows 10.
It looks like some of the links are no longer valid and show error pages in all browsers. However, I've tested other content on Youku, ixigua, bilibili, etc... and they all play in Firefox. I suspect that Windows 7 lacks the necessary (H.264) decoder for the video pages in your list, and other browsers use the built-in library to decode.
Could you please go to https://profiler.firefox.com/ and follow the instructions there to collect a profile? It could help us investigate the problem. Thank you!