Dome lamps inop

This 2000 DiscoII has been reborn and working without any problems for over 3000 miles. This week I noticed that the dome lamps were not working. I followed the wiring back to the fuse block under the dash and verified this circuit with a schematic for this vehicle. It appears that there is an enormous voltage drop from fuse #20 to the connecter on the back of the fuse block. Disassembled, there is no visible signs of damage to the circuit board inside. Included in the rebuild was some welding to the inner LF fender. Does anyone know if this is a typical problem or something that happened during the rapairs? Curious if it is safe to go with a used fuse block or spend more money at the dealer. Any input will be greatly appreciated.