Hi @aprotzman, thanks for reaching out!
Unfortunately the previous user experiencing this issue never got back to us regarding their system specs or additional details, so we weren’t able to continue troubleshooting the issue.
If you haven’t already done so, please ensure that you are running the newest macOS (10.14) and Cinemagraph Pro version (2.6.1)
Are you experiencing input lag, or a displacement of the brush masking from your mouse input location?
Is this happening with all documents or just one in particular?
Are you working with any imported still images?
Lag can occur if you have several other apps open that are straining your devices resources. Closing any unused apps may resolve that issue.
If the brush is displaced from your mouse input it may be caused by a still image’s dimensions not matching your video. In that case, try cropping your video or still image to match the other.
If either of these solutions does not help please list the exact steps you have taken, including when the issue occurs.
I will email you a Dropbox link to upload a sample for us to review. Please include your original source video, editable cinemagraph document file (zipped) and a screenshot of your system overview (Apple Menu>About this Mac)