If I remember, my Stop level drops when the engine is shut off and pumps right back up on its own when started. I played with it a few times, pressing down when it was running, but just to idle down lower. When I let go, the rpm pick up and the lever rises. At some point, the rpm continue drop even though I stop pressing, the engine stops and the lever drops all the way.

I'm going to guess that your Stop lever is not the cause, but an effect, like there is not enough pressure building up in the IP. Since you just did delivery seals, are you sure all are back in correctly, springs 'n things, and the seals are holding?

This is only a guess.

Someone else here should know more about what moves the Stop lever, and what the lever moves...

Best Regards,
Jim