Exported image with heal brush looks worse than preview

In Capture One 22 Pro 15.3.0.100, I used the Heal brush extensively to remove a whole person from a photo, replacing with sky. This edit had several large heal brushes. I got it to look good enough in the viewer so that no-one would notice. But in the exported image an obvious and ugly difference in tone appears, making the image unusable.

This should not happen. Exported images should be faithful to what we see in the viewer, otherwise we cannot trust the software.

See attached images.