Hi, I have been a great fan of Paintbrush on Mac for a long time. now, recently since about last month (Feb 2018), I have the same issue noted by others reported here. Its really frustating and makes such a great software totally unusable. I am running Sierra 10.12.6, and I even tried uninstalling and reinstalling paintbrush, issue still doesn't go away. Thank you for looking into it. God bless.