Strange and intermittent issue rebooting got black screen

I have this very intermittent issue where just occasionally after a zypper dup I reboot and end up with nothing on my screen, it appears to have no signal at least that’s what the monitor shows. A power cycle always boots up just fine immediately following this. I never seem to see this at any other time only following a zypper dup and not always sometimes it reboots just fine. This is a Tumbleweed KDE system running an AMD Ryzen 5 3400G with Radeon Vega Graphics but not using anything other than standard driver packages.

Anyone any ideas please?