I have had great consternation trying to get rid of those horrid grid patterns. I have a ZWO ASI224-MC colour - which says has a Bayer pattern of RGGB. My imaging software is Sharpcap. I was told to put it through Pipp first to do the debayering. Then into DSS for stacking, then into Star tools for processing. Came out awful - grids everywhere. Then I read somewhere to experiment in Pipp with the debayering settings by testing the image, and.....surprise, surprise,,,, when I tested the image with GRBG, the grid had gone!
Back into star tools and all was well - no grid - until I made the mistake of trying to denoise. I got into that screen that says this is a preview. Great...Only there was no way to "keep" or save the image. I tried everything and ended up deleting what was shaping up to be my best ever wide angle shot of Milky Way.
I am now learning Pixinsight (which, when mastered) is streets ahead of any other processing software.
DON'T believe those "experts" who know everything about debayering. Try those different settings for yourself!.
As for Star Tools, well it has let me down once too often.