It could be an issue with the codecs (browsers are usually pretty limited in what they support). You could try to use a client like Jellyfin Media Player instead. It bundles libmpv, so it plays almost any video format there is.

I heard paper burns at 451 °F

Subscribers can expect to see an average of 4 minutes of ads an hour at around 15 to 30 seconds each

Isn’t this a lot? I can’t imagine watching a movie and being interrupted every 5 minutes by an ad.

Do they clump them together and play 8 minutes of ads between the two halves of a two hour movie?