I use Photoshop to sketch pretty regularly, using a Wacom Intuos Pro. I've always experienced this problem and have always just dealt with it, but even I can't ignore something this frustrating forever. I'm wondering if anyone has experienced this problem and has a solution:
Working on a Mac, I use Cmd+Opt+Z to step back while sketching. Needless to say, I step back pretty regularly while sketching. However sometimes (not ALWAYS — which is the most frustrating thing) when I Cmd+Opt+Z to step back, my tool will change from my Brush to the Eyedropper. Pretty innocuous in and of itself, but when sketching fast and having it happen repeatedly (it happens enough where it is a definite issue) it brings my workflow to a standstill and I'm beginning to pull my hair out.
I don't want to simply assign one of my tablet buttons to function as my undo, because as I have my station set up it's much more fluid to have my right hand do the sketching and my left hand resting on Cmd+Opt+Z to step back at a moment's notice. But this random tool change is absolutely killing me.
Has anyone heard of this happening and is there a solution?
"Three things are necessary for the salvation of man: to know what he ought to believe; to know what he ought to desire; and to know what he ought to do."
--St. Thomas Aquinas
Are you still having this problem?
I think I might know what it is, as I was having a similar problem with my wacom in photoshop as well. Are you sure it is tied with the cmd-opt-z? I ask because when it was happening to me it happened all the time, and it was really annoying. Looking back I am pretty sure the problem was that one of the side buttons on my pen was set to "alt", so that I kept pushing/grazing it with my hand without realizing. Very annoying as my colors would often change in the middle of me painting. My memory isn't the best though, so if thats not it, take a look and see if you have the touch gesture options on...I remember turning that off as well, so that might've been it.
Not sure if you've ran into this problem as well but I also found another issue with painting in photoshop w/ the default wacom settings is that there is a setting that basically allows you to longpress with your pen and have something pop up....quite annoying when trying to paint as the pen will stay pressed down for long bouts of time, so photoshop kept trying to pull up some sort of menu whenever I painted.
Anyways, I am getting off topic here, but try to see if it's any of the settings on your pen/tablet first. Hopefully that works...if not, there might be some other things you can try as well.