Greasy Fork镜像 is available in English.
Buffers the video without autoplaying and puts it in HD if the option is on. For Firefox, Opera, & Chrome
< Отзив за YouTube Auto Buffer & Auto HD
I'm guessing this script has been abandoned?
Not abandoned, just don't have much time for it. It's also very hard to fix errors like you're having when I don't have any errors. I appreciate the report, though. I'll try to do what I can.
Video/controls intermittently not displaying, rendering videos unplayable
I'm guessing there has maybe been the usual code tweak to YouTube causing this but thought I'd report it in case I'm not the only one (and now the userscripts site is dead and no one knows where to go to report broken scripts). It is a little intermittent (for example I just opened 20 videos, 5 were broken). Reloading occasionally works but usually when the video content/controls are missing they stay missing.
Using the latest version of the script from here and FF28 (yes yes, I know it's not the most recent version lol)