Iris 2.1b/2.4 LED Fix
For the 2.1b and 2.4 PCBs, there's a missing trace/via on one of the pads for the MOSFET of the right half (the one shown here). To resolve this, solder the MOSFET to the other side of the board, as the pads for those are fine.
Issue has been fixed on Rev. 2.5 PCB, no need to apply the fix to that PCB.
The pads on the other side of the PCB are fine, no need to apply the fix to the other half.