Mpc has strange fault

Hey
I have an Mpc 1000 that is doing some strange things... The 16 level button does not work, when pressing It there is no light or action. I replaced the tac switch and it's still not working. If you hold numeric and press the 16 level it stops the highlight flashing so the tac switch works but no led lights up. If you hold left direction or Rec when holding the 16 levels the 16 level and mode leds both light up. So that means both the switch and the led work but the function doesn't

In short, tac works, led works but it will not activate when pressed alone and it is not possible to use 16 levels.

I have checked all connections and solder points

Has anyone experienced something similar?
I am thinking this Could be faulty resistors on control pcb?

Haven't heard anythink like your experiencing, best bet would be to get hold of a voltmeter to have a poke about on the pcb's to see if somethink has gone on it. Hope you fix it soon