Tuning Capacitor works after cleaning, but goes out again!

[Magnavox300]

Just redid this 1960 GE Musaphonic radio... put in new caps, and resistors as needed. When switched to the phono input, an iPod works clear and perfect, but the radio could not get any stations for the AM.... just crackling and all static... I sprayed the tuning capacitor with Deox, then stations came in clear... after a few minutes went out... cleaned it again with 90% alcohol, stations came in even better, no crackling or popping at all, but after a few minutes, went out again...
still just static and crackling.... wondering why??