Moin everyone,
as I am not allowed to further reply (limit of 3) to this thread SM16714 Pixel IC, I have to continue here.
Moin @jack1999,
at least for my LEDs (Adafruit 4W RGBW LED, I cannot add the link as I am limited to two links for each post) with the mentioned LED chip, the mentioned measures did not help. I have tried 0.14.4 and 0 0.15.0-b5 releases. I have tried any possible RGBW chip supported. Only changing the Uart Method from not-inverted to inverted did the trick to get stable and correct colours on these specific chips.
I have created an according pull request (Add initial support for SM16714P chip based. by pmikka · Pull Request #4221 · Aircoookie/WLED · GitHub) to handle this chip.