Most definitely a short from the hot to the trailer lights, an most likely in the cord as Raz alluded to. Could possibly be a loose wire in the plug like Bob said too. These are is pretty much the only place they are right close together, and a place most likely prone to damage as it is not tucked out of the way, and open to being bruised. I had this happen to me before, and it happened to someone else here last year.
2017 Escape 5.0 TA
2015 Ford F150 Lariat 3.5L EcoBoost
2009 Escape 19 (previous)
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