Dear @hirofumi_momose,
May I know what version is on target before flashing DRIVE OS 5.2.6?
Migration from DRIVE OS 5.2.6 to DRIVE SW 10.0 is not supported. Please see https://docs.nvidia.com/drive/drive-os-5.2.6.0L/drive-qsg-dz/get-started/index.html#update-matrix-drive-os-sw .