This has happened in ZBrush often enough to be an annoyance. I often discover this far enough along that I have to fall back a bit in my file iterations. Does anyone know what this is? What causes it? or whether it will be a problem if exporting a polypaint/model as reference to topogun later? I hate to backtrack and redo what I've been working on and I hate to keep going just to find it turns into a big problem. I'm tempted to keep going and just touch-up later but I can't afford a big time setback.

I am referring of course to the white/red visual artifacts. Also these only seem to occur on the current subdiv (7) but seems not to be effected by turning on or off my surfacing layers. I could drop subdiv 7 but that would cost me a lot of work. Thanks.

There is a chance they belong to a different matcap material. Fill the tool in with a new matcap to see if it goes away.

I've had something similar to this happen before too. If it is the same issue as I had, then filling the tool with white and having only the material channel toggled on should fix it. If not, then I might suggest trying to transfer your sculpt to a newly imported mesh. perhaps even masking those areas out so they don't get ported over. Good luck man, I hope it's a simple fix for ya.