Dithering Gradient tool

While working on a new background i started having problem with gradient tool. The problem occurs only on bigger canvas (currently 1200x500 px). The tool just flickers when attempting to create dithering, changing between primary and secondary colors. While I can create some while doing it in angles, I can’t create any at all when doing so in straight vertical line. I’m pretty sure I’m up to date with software patches.
Have a blessed day Y’all.