You may be able to recreate the symptom by starting a program and apply gentle back-and-forth pressure where the switch plugs into the side of the plastic enclosure. The cause may be that the switch is not fully inserted in the jack, part of the jack may be bent inside so that a good connection is not being made, or one of the wires is coming loose on the back of the jack. Move the coiled cord on the patient switch itself at various points to test for a possible broken wire within the coiled cord.
If the cause is not seen from the outside then the enclosure can be accessed by removing the four hex head bolts (7/16" wrench) that secure the leg cushion. Lift the cushion off. The picture shows the red and black wires that connect to the jack. Make sure the wires are secure to the jack.
