3.0 RC 1(git 6f75b0f)
There are many times when I use my Huion GT-195. When I'm in "Edit Brush" many times the brushes no longer work on the "scratch pad". I haven't been able to tell any consistent reason to cause it. Most of the time the scratch pad stops working when I use the tablet's pen. If I use the mouse, the problem is far less frequently. I can still pick a brush, make changes and use it, but I just can't test it on the scratch pad unless I do all of the operations in the "Edit Brush" using my regular mouse. Once I use the pen, it loses scratch pad preview, either, after a few strokes or immediately. 

Reproducible: Sometimes

Steps to Reproduce:
1.Click on Edit brush and select any brush, Sometimes it won't work immediately. 
2.If I use the mouse first, I "might" see a few strokes using the pen of my Huion GT-195 tablet or nothing will show at all. 
3.Once the scratch stops working, going back to the mouse no longer works either. 
4. So far the only solution is to reboot program and not use the pen when wanting to test changes on the scratch pad.  

Actual Results:  
permanent loss of usefulness of using Edit brush if I want to preview my changes, though I can make changes that will work once I go back to my project. But if I don't like the results, I need to continue guessing or I need to reboot the program. 

Expected Results:  
n/a

n/A