Bleed from radio when playing tape

Our 91 300 SE has the stock Becker 1432 two piece radio. There is a slight bleed-over from the radio when playing a tape. This does not bother my son when he is listening to his Winnie the Pooh tapes and the like, however, my wife is really complaining that it is inhibiting her ability to sing along. She noticed the bleed-over after I pulled and reconnected the trunk mounted piece of the radio for an unrelated reason. I suspect that the problem was there before my actions, however, she now has a reason to blame me for the predicament. Has anyone had a similar problem? Does anyone know the guts of these radios well enough to understand why this might happen?

Like always, befuddled