LT. if you have a cheap multimeter (sometimes Free at HarborFreight, with coupon) , you could trace out all the wiring to see where the problem is ... Having experienced many bad grounds on boat trailers over the years ( exposed to salt water here) , we routinely run a dedicated Ground wire all around , AND to the trailer.... that has eliminated many problems ... Just sayin’ ... And we solder all joins and heat shrink and tape the connections ... a bit obsessive , but pretty much eliminates future electrical problems ..
Good Luck !!!
Ps. Yes doors are Tough ... but the second one always goes easier ... just cause’ you know what to allow for ...

Carpenters have a trick ... Plumb the Hinge line and adjust the frame to fit the door ...

True !!! That allows a little leeway for the structural framing , and flooring not being EXACTLY Perfect ...

That’s why doors come with frames , ALREADY hinged !!!
