Installation crashes while in copy process, grub installer on intel nuc

[Kirsten Dittrich]

at first i tried to install ubuntu core on intel uc which did'nt let me configure network settings, so then i tried to install ubunto 20.04 2 desktop which always crashes on grub-installer, dont know any reason.
hardware is:
Intel NUC BXNUC10i3FNH2
Crucial 32GB Kit DDR4-2666 S0DIMM 1.2V CL19 CT2K16G48FRA266
WD Red SA500 NAS SSD 500GB M.2 2280
WD Red SA500 NAS SSD 4TB 2.5" SATA

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15.10
ProcVersionSignature: Ubuntu 5.8.0-43.49~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-43-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.445.1
CurrentDesktop: ubuntu:GNOME
Date: Tue May 11 23:55:47 2021
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
ProcEnviron:
 LANGUAGE=de_DE.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)