That’s a fairly severe reaction. Be sure your PC is free of heat and power issues.
20 million total between all subtools, or do you have a single mesh that is that dense WITH an unknown amount of layers in addition? You want to avoid especially dense meshes whenever possible. A single super dense mesh is much more difficult to manage than the same poly load spread out over multiple subtools, and may very well cause stability issues. Always aim for the latter and avoid the former wherever possible.
A 20+ million mesh is not super dense, but it is denser than I would have chosen to work with casually when I was on a 16GB Ram system.
And then youve got the layers, and a fairly substantial load of things competing for resources in the background. ZBrush uses a lot of memory, and has very CPU intensive operations. You do not want it to have to compete with anything else on your system. Browsers can start racking up quite a footprint when you have a bunch of stuff open and you’re playing music or videos through it as well.
I can’t say for sure, but from personal experience, it IS possible you’re working beyond the comfort level of your system, depending on what you’re doing.
Maybe, but develop polygon discipline first. Ultra dense meshes will always be problematic to work with no matter how much RAM you have. Deliver more polygons at the base level to high detail areas, and away from low detail areas. Split any meshes that can be logically split into separate subtools. Otherwise you’re simply throwing hardware at bad habits that will continue to hamper you.
Try using the file without any background competition, and see if that eases the situation. If the behavior continues with ANY file in Zbrush, regardless of size, then you should contact Support.