2000 S-Type. Premium sound if that matters

Starting just recently all of a sudden when my phone is played through a cassette adapter it sounds pretty much like a blown speaker. All other inputs (AM/FM, CD) the audio is crystal clear.

I thought the bass, treble etc. settings may have been messed up so I disconnected and reconnected the battery (Display does not work, unrelated), and still the same thing.

Any idea what may be causing this or what a possible solution may be?

 

broken cassette adapter ?

dirty heads ?

phone volume too loud ?

 

I think I would replace the radio. It sounds like it's given it's life already if the display is broken too?
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