The through hole is probably damaged or missing at J115-3.
You can put a wire from J115-3 to F110 or repair/stitch the through hole.

GI 1 (resized).jpg

trace on topside = brown line in picture

Hmm sounds like the through holes have split and are not making contact now. The easiest way is to run a jumper. The hard way is to pull the header and slip a wire in the hole to solder to the trace to the other side of the through hole and then reinsert the new header and resolder it all.

Jumpers are fine. Stitch the hole if/when the header needs to be replaced.

Yes to both questions; just make sure to use an appropriate sized jumper as this is a high current connection (relatively speaking).

I am literally the only person I know of that still performs actual through hole/trace repairs as this requires both advances skills and specialized parts and equipment which doesn't make this type of repair cost effective. The only advantage offered by a true through hole board repair is that when performed properly it's guaranteed to last for the life of the board.

This is what a true through hole repair looks like prior to tinning the new vias:
pasted_image (resized).png

Used to know a guy who did the true repair but he has long since retired. The repair jobs were fantastic and still holding up well over 30 years now!!!

What would be an appropriately sized (gauge) jumper?
Solid wire? (I picture this being the better option from an ease perspective and less risk with errant strands)
Stranded?

I need to make a similar change jumpering the (to be removed) 8 large 6A2 diodes for GI.

16 or 18 gauge is fine. Cheers

Solid or strands? Thanks!

I use a combination of Pace Cir-Kit trace repair kits and solid copper eyelets from a company that closed it's doors a few decades ago.

If I was using a jumper, I would use 18 gage solid wire.