@jyijyi ,
The image size is big is understood but the build should not fail when we change the UBI_ROOTFS_SIZE, current value is 40MB and what I am using is 48MB. I believe this is just a check to ensure an image with size bigger than UBI_ROOTFS_SIZE is not built and produces an error.
but in this case image is not built although the UBI_ROOTFS_SIZE is mentioned 48MB so it should have allowed an image to build upto 48MB in size but clearly that is not the case and seems like there is some additional code added which is preventing it from building in the do_prepare_ubi function of the recipe mdm9x28-image-minimal