Those thin brittle loom wires can only be repaired a few times before needing to shell out on a whole new wiring loom of the same inferior quality, repairing wires on a frequent basis isn't uncommon. OEM digital dashboard backlight ain't so reliable either. Nothing beats an old mechanical analogue for simplicity and reliability IMHO.
*Analogue dashboard assembly part reference: Derbi 864515
*Speedometer cable part reference: 00H01616021
*RX50's with 21" front wheel: Hub sensor part reference: 00H01613051
*SX50's with 17" front wheel: Hub sensor part reference: 00H01614051
Use a handlebar-mounted auxiliary ON/OFF switch, connect either Brown
wire to it. Make a loom and connect it to the bike's battery, run one of the battery wires to the other backlight wire.
The drawback with the old gen analogue is the 80 Km/h 50 mph needle limit. A Derbi Senda 125 unit costs 3 times more. If you own a 2014> bike.. you will have to replace the front wheel with a used or new one from a 2006-2013 model to use the cable-driven sensor.
The other instrument bulbs are unnecessary luxury features that don't need connecting to anything. Unless blind as a bat.. you'll know when the high beam is activated, turn signals flash, and the fuel tank needs topping up.
Once the engine starts cutting out' pull in the clutch lever - reach down and switch to "RESERVE"