A couple things.

1) It looks like you are using the wrong physical size fuse. That looks like a 1” fuse (AGX), not a 1 1/4 inch fuse (AGC). That means the one terminal has less contact surface which could raise the resistance, making heat.

2) It looks like the fuse holder on F5 has been worked on or replaced. Make sure the clips have strong spring tension. If they don’t, that also raises the resistance of the connection, causing heat. It could be possible they were replaced with low current capable fuse clips. If you are going with LEDs, that shouldn’t be a problem as you should be able to install a smaller Fuse.

Bottom line is there is no way that fuse and clip should be getting hot with less than 20 amps running through it if it is in proper working order. The fuse should blow before getting that hot, assuming it’s a 20 amp.

Carefully inspect the molex to make sure the right colors are in the correct position.

Look along the edges of the playfield along each side of the underside of the playfield. When in the playing position, the playfield rests on wooden blocks attached to the side of the cabinet. Sometimes there is wiring running very close to the edge of the playfield that can get pinched when resting on these blocks and short out. I’m not sure is Stars is one that falls in this category.

Carefully inspect the wiring on that string to see if it got pinched. Inspect each socket following along the wiring. Carefully inspect the pop bumper lamp wiring to make sure it isn’t shorted to metal or any of the pop bumper parts.

I would start here. Remove those sockets from the string and see if your problem continues.