Trailer wiring ???

[FED 387]

Bought a used enclosed trailer---all the lights work HOWEVER when you turn on the flashers or turn signals not only do the taillights work on the trailer although not real brite BUT the clearance lights on the trailer all flash and the Stop lite on the cab flashes too---BOTH turn lites on the truck flash but depending whether you are signaling left or right whichever way you signal that lite will be brighter than the other taillite but both are flashing---Disconnect the trailer and the truck is OK--put a new 7 prong plug on the trailer cuz the old one was a little scuzzy that did not help--- The guy I bought the trailler from had just installed ALL NEW Led clearance lites and 2 NEW regular (not LED)stop/turn lites---Anybody got any ideas??? I think I have a pinched wire some where but do not want to tear the whole interior out to find it---He also put new wood on the ramp door but I have no idea if he rewired it while he had that open- Suggestions gratefully accepted--Thanx Comp 387