For Bend Matrix PCB v2.3 and older (versions 2.3.1, 2.3.2, and 2.3.3 can ignore this step).

Flip the board over and solder four 0.1uf caps onto the back side. These guys help prevent oscillations that disrupt the digital chatter between chips.... This step is not necessary for PCB versions 2.3.2 and newer– the 0.1uF caps are already on the top of the PCB