Sound is garbled on VCR?

Sometimes when I play a recorded tape, the sound is garbled. I tried the tracking control, but it does nothing to the audio. Sometimes when I fast forward it for a couple seconds, the sound normalizes. At first I thought it was because the tapes were getting old. But recently, I recorded a show and the next day I played it for the first time and the sound was garbled. This time it eventually leveled out after about 3 minutes. It is fairly old VCR; it's atleast 5 years old. Is the VCR dying, or was a bad tape?

PS - The audio distortion doesn't sound like anything interference would cause, either. (I get my signals through a tower antenna)