When I perform grayscale release, the image used for the grayscale version cannot be changed.
When performing grayscale release on a service, you create a new version of the same service. Therefore, the image used by the service cannot be changed. Only image tags can be changed.
Pack the required image into a different tag of the same image and push it to the image repository. Then, select the newly pushed image tag when you perform grayscale release on the service.