does this happen when you use it for any project no matter how big it is?
Is this the only tool giving you problems? Btw, which version of the application are you using?
I am currently using version 1.2.1.
I just tried it with a smaller project and the loading wheel did not appear but the brush seemed to have lagged on the screen. It returned to normal after about 20 seconds.
Yes, I have used all tools and this is the only tool that makes it happen.
Can you please let us know the difference between the smaller project and the one where you encounter the issue?
Can you e.g. give some info about canvas/image size and amount of layers?