I changed my side lights to led and I noticed there were tons of small rocks. Ford should have installed some kind of liner to keep water and rocks from hitting the wiring and assemblies. This is something my Accord had right
I went thru miles of freaking loose gravel, so don't even want to look there. Ha ha. But glad you mentioned it. Will check both fenders (probably where there are a lot more), and the reverse light. I have the DD LED side markers, which are great, but I didn't like that the plug is super loose, basically making zero pressure on the O-ring (the factory plug is super tight, as it should be), so water might get in there. I guess will find out when I drive the car in the rain.