Totally Forgettable Movie

I don't mean this to be rude, I'm just wondering if anyone else has had the same experience as me - finding it impossible to remember this film.

Normally, every movie I watch I remember in great detail - scenes, dialogue, plot, characters, themes. Even if it was twenty years ago and I only saw it once, I can remember what clothes people were wearing, key lines in the movie, all sorts.

I've seen Lethal Weapon 4 three times now, and the only things I can recall are that Murtaugh hides some Chinese people in his house, he and Riggs fight Jet Li on a pier, and Chris Rock gets annoyed when Leo calls him a 'perp', pulls out his piece and shield and says, 'Here's my badge, here's my gun'. And that's it.

I can't remember family, kids, subplots, or the main plot, haircuts, what they were wearing, any of the jokes, any of the dialogue. I think Lorna was in it, but if she was I can't remember her, nor Trish or Rianne or Nick. If you asked me what the movie was about, I wouldn't be able to tell you, and I've watched it three times.

This is the only movie I've encountered that is totally forgettable - I watch it and I instantly forget everything I just saw, and I have no idea why.

Has anybody else had a similar experience?