Hi again,
Don't worry about posting in the other forum. It
takes a while to figure out the best ones to post in, depending on the
subject. It's easy enough for me to move threads, and it didn't take
but a minute.
Not being a Mac user, I can't help with that end
of the problem, but the first thing I'd do is to call Wacom to see if
they can help. That I did, and coincidentally the tech support person, when I described the problem, told me he remembered talking to you. He said he'd suggested using Edit > Preferences > Brush Tracking but he guessed you might have thought he meant something in the Wacom Tablet Preferences.
What he was referring to is within Painter 7 (and other Painter versions) and if it's like Painter IX and Painter X, the menu is Painter 7 on Mac rather than Edit in Windows:
Mac - Painter 7 > Preferences > Brush Tracking
Windows - Edit > Preferences > Brush Tracking
In Brush Tracking dialog box, paint a brush stroke on the Brush Tracking scratch pad using your normal hand pressure and speed, then click the OK button. This will reset your Brush Tracking settings to match your own normal hand pressure and speed and it may be the solution to your problem.
Like the rest of us, you may need to reset your Brush Tracking every now and then, sometimes for a specific brush variant to work the way you want it to, sometimes just because we don't paint the same way every day due to how tired we might be, for instance.
Let me know if this helps.