It is possible the "up" solenoid (relay) is flaky. You could swap it with
"down".
The bypass is just a screw that releases pressure when you are going to open
the hydralic system. They should show you where it is in your owner's manual
and that may be on the net.
I rebuilt my Merc unit several years ago and it is pretty complicated. Lots of
little rubber parts that they sell for huge bucks. If you wrinkle an O ring or
cup you will have to start over.