i keep getting videos on my fyp that i apparently have saved but never seen before??

Hi, i often get videos on my fyp recommended that I apparently have saved before (the save button is yellow) but I don't remember watching them?? I thought maybe I don't remember watching them but just now the same happened again with a video where the oldest comment is 17 hours ago and I'm so sure I would at least remember that far if I watched that video or not and I know for sure I did not. Is this a glitch? 😭