Really weird playback problem Premiere Pro

I always shoot videos with my Iphone and I´ve made 4 aftermovies like this with no problem. Now suddenly the playback does this weird thing when i put videos in my timeline and watch it, it´ll randomly start playing from the beginning of the clip, even though the blue bar keeps going! It´s not lagging, because when I go through it frame by frame it will still randomly show the beginning of the clip in the middle of the actual clip. I´ve tried rendering in-out, making a proxy but that doesn´t change anything. I´ve even deleted premiere pro and re-installed it, cleaned my laptop (all the basic stuff you do as a nontech guy) but I'm out of ideas. Hope someone can help, thanks!