Automatic 1993 Honda Civic EX Coupe "Shifter Problems"

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I have a Automatic Transmission 93 Civic that has been having problems shifting out of Park. My computer and main relay went out a little while ago, when I got them fixed, the car would not shift out of Park. I have to use the shift lock release to put it in Neutral. From there I can shift all other gears just fine. If I put the car into Park again and hold the brake it will move fine still, but once I put it into park and then let go of the brake, it sticks and I have to use the shift lock release again. It's only been like this for about 3 months. I plan on selling the car now, but would like to fix this first so as to not have any problems selling the car. does anyone have any idea of what this might be? I think I know but I would like a second opinion. I have read and talked to my dad, who is a tow truck driver, who deals with damaged cars all day and has always been great with helping me with car troubles, and we think it is the shift control solenoid. Any thoughts?