Turris OS 4.0.1 is out!

I have updated my Omnia to 4.0.1 , but I´am facing a problem with add-on NetBoot for my Mox.
Under 3.11.x Mox was shaky too and I have some experience to get it running, but under 4.0.1 I don´t have luck. After reinstalling “NetBoot-Addon” under Foris I get this Error:

Error from 2019/10/17 12:22:02
Updater failed: Failed operations:

turris-netboot-tools/postinst: udhcpc: started, v1.28.4
udhcpc: sending discover
udhcpc: no lease, failing
Regenerating configuration…
Getting new rootfs…
Downloading ‘https://repo.turris.cz/hbs/netboot/mox-netboot-latest.tar.gz’
Connecting to 217.31.192.69:443
Writing to ‘/srv/turris-netboot/rootfs/rootfs-new.tar.gz’
/srv/turris-netboot/ 4% |* | 1759k 0:00:22 ETA
/srv/turris-netboot/ 100% || 42066k 0:00:00 ETA
/srv/turris-netboot/ 100% |
| 42066k 0:00:00 ETA
Download completed (43075675 bytes)
Downloading ‘https://repo.turris.cz/hbs/netboot/mox-netboot-latest.tar.gz.sha256’
Connecting to 217.31.192.69:443
Writing to ‘/srv/turris-netboot/rootfs/rootfs-new.tar.gz.sha256’
/srv/turris-netboot/ 100% || 98 0:00:00 ETA
Download completed (98 bytes)
Downloading ‘https://repo.turris.cz/hbs/netboot/mox-netboot-latest.tar.gz.sig’
Connecting to 217.31.192.69:443
Writing to ‘/srv/turris-netboot/rootfs/rootfs-new.tar.gz.sig’
rootfs-new.tar.gz: OK
/srv/turris-netboot/ 100% |
| 151 0:00:00 ETA
Download completed (151 bytes)
Cannot open file ‘/etc/opkg/keys//XXXXXXXXXXXXXX’ for reading

Tampered tarball

What is the Problem? Can anybody help me?