Hi, welcome to the forums. My guess is the fixtures you have have a low quality LED driver with low refresh rates, so you need something that has a higher refresh rate. I would have you look at grabbing just one of these to test with: https://www.eliminatorlighting.com/mini-par-rgbw-led
They are pretty affordable at 29 bucks MAP price each. they have a really nice white and they do color mix with RGB, you'll get more of a tighter wash coverage instead of a flat field "spot like" coverage with these, but they are a good price to test with.
Also we have not heard of anyone telling us these Mini pars flicker on videos.
Here are a few example of them on the Eliminator booth at various tradeshows (Eliminator is a sister brand to ADJ for the low-to mid level budget, but STILL quality)
There is actually one running inside of a white scrim table throughout this whole video.... but the rest are in the center of the triangle truss in that video.
This video they are on the truss going vertically up and down on the back, you'll see them as you can see the individual red green and blue leds and the white. But they color mix in the air just fine.
Does this help, do you need me to point you to a dealer for you to purchase them? We don't sell on Ebay.