I'm glad the OP figured out the problem and it was a simple fix. But one statement he made really made me laugh!
"We had our daughter try it barefoot also and as long as they are standing barefoot on the ground when they touch the metal on the trailer they get shocked. And it's not just a little trickle is a good jolt."
I can just see it ....
"Go ahead daughter ... touch it! It's OK, just touch it!
"I don't want to... I'm afraid!"
"It's OK, it won't hurt you!
ZAP! Ohhhh!!!
"That's OK ... go ahead ... do it again! Really, it's OK ... do it again!"
"But Dad!"..."But, but, but...."
"Now sweetie, just do it. It's all in your head!... go of it ... GO!"
ZAP! ZAP! (Ohhh... OHHHH!).
"Very good Dear ... now, just one more time!......" :B :S
I knew we had kids for a good reason!