iMac (27-inch, Late 2013) Crashes When Running Optimize Now/Brush Accelerator

Hello, 

I have a iMac (27-inch, Late 2013) with a NVIDIA GeForce GTX 775M 2 GB running 10.14.5 (so the latest MacOS) and it crashes every time I try running Optimize Now/Brush Accelerator:

See video: 

https://www.dropbox.com/s/bzksushdzoqvwb2/Crash%20Demo.mov?dl=0

It's a clean install of the fully licensed version. 

Any one have any ideas?

Thanks, 

638ways.