After 20.04.3 Upgrade, at shut down screen locks up

Ubuntu-20.04.03 LTS, Ryzen 5 4800x

New install, all ran perfectly so I rebooted and did an Update; followed by an Upgrade. used it a while then shut down -- all good.

Restarted and again, all good until I tried to shut down. Screen went full moving-pepper&Salt and system locked.

I forced a hard-shutdown, restarted and selected "Additional ." and the 5.8 Kernel with no problems since, so I deleted the 5.13 Kernel.

I suspect this is a Ryzen graphics thing, but I would like to use the 5.13 Kernel that was installed with this and future Upgrades.

How can I fix this?

Thanks

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