Sounds like the loose connection is at the bolts where the jack bolts to the frame of the TT hitch area. Possibly some cleaning is needed where the bolts are, I would (while TT is mounted on TV) unbolt the jack and thoroughly clean the area where the jack touches the TT hitch area so you get good metal to metal contact (on my TT this is the ground that completes the electrical circuit) then tighten the bolts up good.
Dale & Terri, Lulu & Tiki (our Chihuahua's), New rescue puppy Prince - Pom/Pug mix.
2013 Tundra, Double Cab, 5.7, TRD Off-Road, 4X4, Full Tow Package
2013 Wildwood T26TBSS - Sold
2000 Gulf Stream Sun Voyager M-8357 MH, Ford Trident V10 Gasser, 35 foot.