Can Someone Please explain Cyl #2 Missfire

I have a 2016 Wrangler 75th Anniversary edition, two door hardtop, Sahara, V6, 37000 miles. Long story short Cylinder #2 MISFIRE code came up and after trying several things it ended up at the dealership. Diagnosis was "valve seat overheat. Head needs to be replaced and thermostat is sticking". Over temp light has never come on. I don't have to tell you what that costs. I told them to go ahead but after reading some and being concerned with the sand in the cooling system issues of the past I told them to reverse flush they cooling system. Today the rep became involved. They told me no sign of sand. I said ok them check the temp sensor because the light has never come on so it must have gone bad. They said they doubted it was bad. I may have been born at night but it wasn't last night. If sand wasn't the problem and the sensor is good and I assume they checked for a blown head gasket then WTFO. So I tell them I want the old head. Call me curious. They said since it isn't warranty then its yours. On a subsequent call I'm told no no no you have to pay $150 disposal fee. Well now my spidey senses are tingling.

From what I have read in various posts and forums Cylinder #2 misfire is not uncommon but in my opinion too common. Can someone give me a definitive answer as to what the cause is for the " valve seats to overheat". For what I paid to have this work done I'm beginning to get the feeling that when I go pick it up there is not going to be a cause they can point to. BTW I'm paying the $150 to get the head back. I want to see the look on their faces because something stinks.