Does it appear all the time or it comes and goes? If it comes and goes I would say it could be the camera cable (or bad connection) which is about 20$ if you DIY.
Hello and good day tofa. I am sorry to know that you had an issue with the photos captured by your DJI Mavic Pro and it is great to know that after doing a factory reset and re-calibrating the said drone the issue was fixed. Please stay safe always and keep on flying.