I have a 2001 model and when I put the key into the key holes on the outside of the van (any of them), it unlocks the two front doors, the rear hatch, but only unlocks one or none of the side sliding doors. These are manual doors, not the power assisted ones. The problem persists with the locking and unlocking buttons on the front panel inside the van; locking or unlocking the doors only works for the front two doors and the back hatch, but only sometimes unlocks the side sliding doors. Any ideas why this could be happening or what could be causing this issue? Loose wires? Fuse replacement? Any electrical components that could be failing?