Are they the black plastic sockets that twist into a circuit board ?

If so, remove the light board. Reflow the solder on the pins the connector plugs onto. Reassemble. Live happily ever after.

LTG : )

They have one common wire. Check continuity of it from light board to board in the head, and be sure you have a solid connection to the board in the head. Then measure power leaving the board on that pin in the head.

LTG : )

Had another thought. Measure power to the board. If it's good, then suspect your small twist in sockets. The part in there that grabs the wires on the base of the bulb might be loose or corroded.

LTG : )

Either the LED contacts, or the metal things in the socket that should grip it tight.

LTG : )

Put a meter on the connector and see what is going on. No sense chasing back and forth until you isolate the exact point where you lose power. Leaving driver board, at connector of light pcb, at socket, at bulb.

LTG : )

If those lamps have a wire color common to all of them, you have a weak connection or solder joint somewhere along the line. There, or at other lamps of the same color.

LTG : )

Yes. At this point I'd grab a meter and check from the driver board to the connector on the pcb the sockets are snapped into. Try and figure along the way where you are losing power.

LTG : )