fails to boot in legacy mode

[xikoqofa]

Hello,
We're currently experiencing an unusual behavior of some of our machines. If the HP SPP (for upgrading the firmware) is booted in legacy-mode (UEFI works fine!) kernel messages are displayed, stating multiple "CPU soft lockups" and the system remains in an unresponsive state.
What could be the reason for the image not booting properly on some machines while others with the same HW-configuration load the image perfectly fine?
Thanks in advance.

[Ash_1711]

I suspect the mini Linux kernel the SPP may have some sort of issues when the boot mode is "Legacy BIOS"  Switch to the UEFI mode before doing the SPP firmware update & clear NVRAM & check, if issue persist try with a different version of SPP image.