Hi Dee anne,
Regarding the issue, does it occur when adjusting the Depth Control or Portrait Lighting? If you're unsure test the steps below found in the article here: Use Portrait mode on your iPhone - Apple Support
"Adjust Depth Control and Portrait Lighting
After you take a photo in Portrait mode, you can adjust the level of background blur and the intensity of Portrait Lighting effects.
- Tap a Portrait mode photo in your library.
- Tap Edit, then tap the Depth Control button at the top of the screen to adjust Depth Control or Portrait Lighting button to adjust Portrait Lighting. A slider appears below the photo.
- Drag the slider left or right to adjust the effect. A gray dot above the slider marks the original value for the photo.
- Tap Done."
Should the issue continue, and occurs no matter the image zoom or Portrait Lighting, reach out to Apple Support directly to further assist.
Contact - Official Apple Support
Contact Apple for support and service - Apple Support
Best.