LEDs flashing their current color brightly every few seconds.

I am experiencing random color flashing. Please see the video below for an example.

The screen that the leds are mirroring is on an unchanging view.

I have tried turning smoothing off and on with no changes seen.

I have changed the brightness to 50 and 75% to no avail.

I am using a 10 amp power supply for led power. I am using a FCOB led strip. (36 leds per 1 ws2811 chip)--> This means there are 100 ws2811 for a 5m strip. I am using 100 inches (2.5 meters) of the LED strip. Using half of the strip, I am controlling 50 WS2811.

The strip is 12v

I am using a pi4 connected to an arduino nano by usb which then has the data line of the nano connected to the data of the led strip from pin d6.

I'm not sure I completely understand the idea of a "common ground". My ground connections are as described below:

ground from arduino goes to negative of the 12v power supply that is being used to power the LEDs

I have a usb coming from the pi going to power the arduino (does this count as the ground between the pi and arduino?)

I have a usb capture card connected by usb to the raspberry pi.

If so, I have a common ground between the leds, arduino and pi.

Thank you all for any troubleshooting you can help with. This is driving me wild.

Thanks again!!

I couldn't attach a video of what is going on so I have put it at the google drive link below:

Video.mov

Video of effects doing the same thing/ random bright flashes of proper color and location of the effect- 5 second mark- happens at different locations points in effect:

Video2.mov

Update:

So I hooked this set of lights up to a WLED controller that I had laying around and the leds seem to be working perfectly with constant color and effects so hopefully someone will be able to help me pinpoint what is going on in my installation spoken of in the first post.

I would really like to remove the arduino from the equation as long as my retrogaming (retropie) won't suffer due to increased load/ processing being placed on the pi after removal of the arduino.

I also am trying to stay away from wifi communication in an effort not to ruin my network speeds.