Noticed today when checking the actor collection that a few Movies I know I have marked as watched were still UN-ticked and visible even though I have hide watched selected!
I backed out and re-autherised trakt. Same results, I checked trakt and Yup marked as watched. It wasn’t until I searched for the movie using the search function did it come up in my list with a tick on it, after that I went back to the movie collection and it’s now ticked as watched. I had to replicate this with several collections and some from the same actors.