The hybrids go bad these units and will exert the same symptoms you see. 

this is AFTER a recap BTW. 

A quick fix is to put a 1 Meg ohm resistor between pins 18 and 16. 

Also, there are pull-up resistors ,and 1 UF capacitors that attach to both the NMI and Reset buttons, if they go bad, or if there are broken traces there, the same thing will happen.