vts mechanical
have you checked the linkage ans screw for binding???? lube with silicon grease.
also have you looked at the motor??? has it gotten wet and corroded?
also when you press the up switch do you have a faint click from inside the vts module?
i've been working my 96 gsx. it had blown the fuse in the electrical box and the motor doesnt get power to move when that happens, but the point is, when i'd press the up or down button i would hear the click of a relay from inside the vts module and the point to that is, it confirms that vts module sees the swithes (both). in your case your down work but your up switch might be bad. prove it out by listening for the click. good luck, keep your head clear.