I just wired up the following schematic and both sets of LED recessed lights will flicker when dimmed below full power. It doesn't matter what the other dimmer is set to (full power, low power, off). The flicker is very quick, it is sporadic and doesn't follow a pattern. All lights on each line are included in the flicker. When set to full power on the dimmer slider, no flickering occurs. Both of the dimmers are the same and they are listed as compatible on each set of lights. All of the wiring that I ran was 12/2 based on this being on a 20 amp breaker.
All of the LED lights come with junction boxes and screw on pigtails down to the actual light. In the set of 4 LED's on the left of drawing, I have all 4 junction boxes wired up, but only the last light is connected by its pigtail as the wife wants to wait for the countertop to be installed before deciding how many lights she actually wants over it. So I may be removing a 1 or 2 of those lights from the line.
The middle switches in each 3 gang box are simple on/off switches to run either a ceiling fan or an exhaust fan.
I am curious of what steps I should take to try and diagnose the flicker. I just rechecked all wiring connections and nothing is loose.
My thoughts are that either the three missing lights on run one are causing the flicker. Or the USB outlets sharing the neutral line are causing the flicker. Or the dimmers, even after being listed as compatible actually aren't.
Is there anything in this schematic that jumps out to someone before I start buying different switches and outlets to troubleshoot with?