I had the same problem on three servers running with an AMD EPYC 7402P 24-Core Processor.
After removing the amd64-microcode 3.20191021.1ubuntu0.18.04.2 package the servers did not end up in a reboot loop anymore and were able to boot.
I had the same problem on three servers running with an AMD EPYC 7402P 24-Core Processor.
After removing the amd64-microcode 3.20191021. 1ubuntu0. 18.04.2 package the servers did not end up in a reboot loop anymore and were able to boot.