Broken AM /FM switch in Delco radio

[Nellie]

My 87 C10 has the basic AM/FM delco radio. It was working fine, but recently the radio is stuck on AM. When I move the AM/FM switch, it goes from AM to FM when the switch is in a sweet spot in the middle but then goes back to AM when I move the switch all the way to the FM side. I try to leave the radio in FM in the middle sweet spot, but the switch will move out of that sweet spot and back to AM when I hit a bump. Any idea's on how to fix this?

 

[1987 GMC Jimmy]

Delco 2700s are a largely mechanical apparatus so I'd assume some kind of worn mechanical contact. If it were me, I'd Google radio shops that work on them and ask them what they think.