Interesting!

On your flipper board, does the LED stay on when you push the flipper button in?

More importantly, do you have a Rottendog replacement flipper driver board?

Take the glass off your playfield, get the flipper to stick. Push the flipper back to rest position. Is it being held with a strong feeling buzz, or does it 'break back' with the slightest encouragement?

The correct flipper return spring is QUITE strong. Did you somehow get a weak return spring? The correct spring number is 265-5029-02. I definitely had this happen with a machine that someone had put weak (Williams) flipper return springs in. I suspected that the plunger was getting magnetized to the stop, but since the stronger return spring fixed it, I didn't look further.

This could be a combination of EOS switch and marginal/bad parts on the Flipper driver board. The EOS switch on Data East Jurassic Park is... challenging. Make SURE that it is REALLY tightly closed, and is the correct part. The correct EOS should be part number 180-5124-01, and be adjusted so that when the flipper is engaged there is about a 1/16 gap. Contacts on this switch frequently need to be cleaned with Alcohol fresh from the factory to make sure they making very solid connection.

Let us know what you find!