May want to use a cable tester as well to help track down the issue. I picked up something like this at Menards for about $20 IIRC
Sperry Instruments TT64202 Cable Test Plus, Coax & UTP/STP Cable Tester - Detects: Shorts / Miss-wires & Reversals, Wiring Reference Chart Included, 2 Pc. Kit, Yellow & Black
https://www.amazon.com/dp/B004Y75B5Y..._THDtDbAVCGCSX
Have had loose connections on the switch box as well.