I have been playing my VHS tape from my Panasonic player into my TV when suddenly the next tape does not play anything but static and the sound track! I thought it was the heads. But bought a cheap 2nd machine whiile the first went off for repair. The same thing happened with the 2nd machine!!!
You are putting dirty or damaged tapes in and clagging up or damaging the picture head. Try looking after your tapes (e.g don't leave them on the floor) and using a head cleaner.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cassette recorders.