I've noticed that the videos on the site (in the Sam and Max section, specifically) don't load while they're playing.
If I press pause, the rest of the video will download very quickly. If I press play before all of the video is downloaded, the download will stop at that point until the playback reaches it, then the video will automatically stall and a little bit more of the video will download, then it will repeat - play, stall, download, play, stall, download.
So far I've found my best option is to immediately pause the video and allow the entire thing to load, then play it once it's reached 100%.
I'm using Firefox 188.8.131.52 on Windows XP Professional.