Hi,
This issue is reproducible on some specific devices only and is being investigated and tracked internally.Any progress on this will be conveyed.
Meanwhile if it is not a problem for you, could you please uninstall the driver for tablet and Flash(Use CC cleaner tool) and re-install the latest version of drivers from Legacy Drivers | Wacom and also Flash Pro CC 2014 from Creative cloud. reboot the system and check if the issue happens??Because most of the times updation of the driver has helped resolve the issues related to brush.
Thanks,
Sangeeta