I have heard it time and time again, don't tape over old footage. Break down and pay the 8 bucks for a new tape. So here I am wondering why after playing back the tape from an interview I shot earlier today, there was about a 5 second period where the footage I had taped over was now playing (through bands) instead of my interview. I guess its just one of the lessons you learn as a rookie but I would like to understand technically what causes this. Is it from lack of proper cleaning or re-using the tapes or ?

It could be a point in which the heads dropped out and didn't actually record for those seconds. It's like the old days of using an audio cassette over and over until while playing a song one day you can hear a previous recording in the far distance on the speakers.

So if that is the case I am wondering if the same thing would have happened with a new tape and would have therefore been black for a few seconds?