I have heard of problems when the frame rate as tagged/stored in MC is wrong (for some reason), perhaps take a look and be sure it is not set to 50fps when it should be 29.97fps, or some other value. In some other posts, Users have said they deleted the entry stored for FPS in MC and the playback improved. You can check in Standard View >Video>files (just right click on the column header and "check" the box next to FPS see the FPS values for each file).