Will it work reliably motionless, say running on a flat surface with no one touching it? If it does, you likely have a faulty ribbon cable in your hinge. Once they get touchy, they get so twitchy as to be unusable.
We fix those by replacing the entire top half of the DS, hinge top screen and all. Going inside the hinge is VERY labour intensive. Plus that twitchy ribbon cable is wave soldered to the top screen anyway, and cannot be removed from it.
Hopefully I'm wrong, because that is not an easy fix, and requires a donor DS Lite.