Tandberg 420A. Cassette Deck - sticky help help please

Greetings fellow vintage cassette deck lovers >

I have a Tandberg 420A cassette deck, that still sounds terrific !!  My problem is that the Function Keys are "sticky"... they are difficult to press, and the Pause key does not easily release when pushed to do so...yes....I took the deck apart and tried to clean and lubricate the best I could....This model has all of the Keys on a Track, that may be my issue. 

Are there any knowledgeable 420A members out here ?? Your comments and help would be greatly , greatly appreciated.

Thanks again,

Gustard

New Jersey