Beau is Afraid was the last one I recall. I think it was mostly the latter half of the movie where I started to get a bit confused and needed the ending explained to me.
What movies made you look up some kind of explanation afterwards? I feel like I have done it several times in the past for more surreal movies but can’t think of any other examples.
It can also be a TV show.
I mean, it was groundbreaking for its time and it redefined the genre and a lot of moviemaking in general, but it really didn’t age well as far as moviemaking goes. Yeah, it has severe pacing issues, is undeservedly way too long and it got way too trippy and abstract by the end. Frankly a whole lot of it feels like Kubrick masturbating over how great he is, with a lot of scenes being way too long and serving no real or useful purpose on on the movie.
I could say pretty much the same about Solaris too (the original Tarkovsky version which cinephiles always rave about, not Soderbergh"s, which I actually prefer), and if rumors are true, apparently Kubrick took a lot of ideas from it.
And I say all that as an avid sci-fi fan. The books from Arthur C. Clarke are more enjoyable.