Note: the injector pin can be cleaned without removing the pneumatic tubes or the Viscotec assembly.
Remove the 3x M2 hex screws with a 2mm Torx screwdriver to remove the valve assembly from the mixing body. Note that only one valve assembly is shown, but this procedure can be done for all 4x material valves and 1x purge valve.
Inspect the back of the valve and clean off any debris that is present on the tip or along the pin.
Place back into the mixing body and secure with the 3x M2 hex screws.