The only time I've heard it jump like that is when dd gets an error writing to the disk/partition. Usually, it is a bad sector, or that the disk/partition is smaller than the original. g4l impages can be restored to teh same size or larger disk/partitions. It is a bit level backup, so that is what I've seen. Don't have NVME disks to test it on, so have only used the virtual box disks, and seemed to work just like the normal disks.