Video Files Don't Play Back Properly

I am a novice on Premier Elements 2020, although I have used Elements for years. I can get video files (.avi and .mpg) added to my video project ok, but when I play them back, there are 2 problems: they play too fast, and the audio has a constant, rapid clicking / tapping sound along with the normal audio. These files play back fine on the other media players on my computer (PowerMediaPlayer, Windows Media Player). I am using a Windows 10 desktop, fully up to date. I assume I've got something set improperly, but I don't see what. Many thanks for any help you can give.