that's what it's supposed to do
when you are elevated you do not want to move fast, when the boom/scissor is raised the unit is less stable and could turn over if you hit a pothole.
they are set that way for safety reasons

now if it is moving very slow like creeping there may be a traction control switch on the platform control that is normally used for either driving on flat ground which is the fastest or if your climbing a ramp or going up a hill it gives it more torque but will move a little slower. With the grove lifts that switch may not be there on a 95 model and the speeds are totally controlled by the safety switches on the boom/scissor. By design you move it to where you are going to be working fully lowered, then when you raise it up to where you're working it should move slowly so you can adjust position if need be but not fast.

But just FYI, DO NOT bypass them

And just FYI again, Grove Manlift Division is no longer in business, Minpar took over the parts sales so you can still get parts but anything beyond that is a crapshoot. If someone here has service literature on that model maybe they can help. I do not.