Healing brush size changing automatically

When using the healing brush, the brush size is automatically decreasing as I use the tool. I am on a Mac 10.15.7. The behavior occurs in the current versions of the software, as well as earlier versions. I am also using a Wacom Intuos Pro. I uninstalled the Wacom software to see if that would make a difference, but the problem continues, regardless. Any help would be appreciated!