Looking for feedback on how I have run my lighting;

1st Gledopto is running on 12V powering around 600 LEDS per GPIO02 and GPIO016 Channels

2nd Gledopto is running on 12V powering around 200LEDS on GPIO16

3rd Gledopto is running on 5V powering 150 LEDS per GPIO02 and GPIO016

4th Gledopto is running on 5v powering 65 Leds per GPIO02 and GPIO016

I am having issues with the 2nd Gledopto box outputting a random string of colours and flashing lights to the 200 LEDs which it is connected.

When the output of 2nd Gledopto is connected instead to the first one, everything runs smoothly.

I think my issue is lack of common ground between the 1st and 2nd boxes, but maybe I am completely missing the mark. 

This is my first project, in my mind more controllers were better and due to an issue with ordering 12V and 5V SK6812 I needed two separate power supplies.

I am running power injection at the ends of both the 1st Gledopto lines and have been happy with the results thus far.

I also believe I should be running fuses between the power supply and all the Gledopto boxes. It has been working fine but I also understand that things work up until they dont, and when they do not, it can be a hazard.

Would love any feedback and have been excited in learning the processes of soldering, WLED, and base DC current knowledge.

Am I Missing Something?