@Donatzsky is correct. The pattern is due to lens correction shifting pixels around. Here is an example, of applying a lens correction to noise, with the pattern enhanced.
What is happening is in some places the lens correction needs to shift pixels by fractions of a whole pixel and in other places pixels are not shifted or shifted by whole pixels. When pixels are shifted by a fraction of a pixel, the result is a slight smoothing, which reduces noise. When pixels are not shifted, or shifted by whole pixels there is no smoothing.
The result is noise is smoothed out in a pattern, such as the one you can see.
The solution to an obvious pattern is to reduce the noise. Some demosiacers have less obvious noise than others, so that is an option, but selective application of noise reduction and sharpening (or not sharpening) is your best bet.