Cycles left some squares in final render does anybody know why I get this final render in CUDA Cycles. I get this results when I try to render with CPU and GPU together, like they have set different number of samples or CPU try to catch up the GPU and don't render all samples:

GPU or CPU only render doesn't leave those squares, but what is interesting is that number of sampling doesn't change anything...I get the same noisy render when I set 400 samples and 20000 samples and the render time doesn't change, in both samples cases time is the same and I couldn't achieve better results.
I use latest Blender version 2.92, CPU Intel i5, 16 GB of RAM, Nvidia GTX 1050 Ti...win 10.
Is it possible that some features of Octane render engine, which I try day before and uninstall afterwards, has left behind and messed up my cycles render?
I have just noticed that the number of render samples are somehow limited to 32???
Any Idea?
I have found out what cause the problem!!!
One of my area light which I have use to imitate lights of the wall lamp, has been partly inside of the object:

That cause the artefacts and lot of noise. Now, the image is crystal clear!

I hope this will help others with same problem ;)