Unwanted AutoPlay and Full Screen mode in Safari

iMac M3 chip Sequoia 15.5

Safari 18.5

Not always, but frequently enough to be bothersome, Safari goes into Full Screen mode and auto plays videos on websites. Despite having set autoplay to Never and Block and Notify for pop ups. It is particularly bad on the Rivian website, but not limited to just them.

How do I correct this?