Artifacts when rendering 4K in Main Concept

[Tom Ross]

Thanks Danny…will do

[Artem Gummed]

Hello !

I have the same artifacts as this video !!

Artifacts problem Fluke Hall

wow Im not the only one !
I bought a month ago a Radeon HD 6970 for fast renderings using the OpenCL. and it worked fine , actually very good!!
I was rendering Full HD videos and 4K videos from my Panasonic lumix GX85, but one day I turned off my PC and took out the graphic card to insert it in to another system (for testing) installed drivers , etc .
Rendered one video , but didnt verified the quality. Then I put it back on my main PC where it was, and when rendering 4K videos , I have always those ugly artifacts :(((( I was so happy not even with the 2nd system is the same

Used cpu only rendering and its fine but very slow
I dont want to wait 10h to render a 30min video

While testing to render fullhd 1920×1080 there is no artifacts everything is clean
only 4k is the problem …
tried different drivers, no change
tried Handbrake, its good, but not as fast as with OpenCL

is there any one that can help me fix it ? help