JD2010, Kubota3450,2550, Mahindra 7520 w FEL w Skid Steer QC w/Tilt Tatch, & BH, BX1500
Appreciable tension combined with the added stress of flexing it into the wrap. This can overstress the portion of each strand that is on the outer part of the curve resulting in slight bending and the set into a spiral. No point in trying to fix it as it would happen again anyway. The lay up of cable onto a drum has to be well controlled to prevent rub points and cable crossings that accentuate the flex/bend and I doubt small winches provide for this.
I never had winch cable coil up BUT as it got old and used a lot - it would certainly start fraying. I never had a frayed winch line snap either. HOWEVER - a frayed winch line will pull the frayed ends right thru a pair of heavy gloves and can really cut up your hands.
Its never a good idea to allow a winch line to slide thru your gloved hand for any reason.
For maintenance - at least once a year I would remove the cable from the winch drum, spool it into a five gallon plastic bucket and let it soak in used motor oil for a day. This was a messy operation but it seemed to help the cable maintain flexibility and resist any rust. Now there are products specifically made to spray on/soak winch line.
Mine usually starts fraying near the end, I cut it back to the good part and re-clamp, if I get down to around 70', I replace. When I start getting wood I put some grease on my sliders