system boot order not found Peppermint

[holdfast]

Can you help me with a problem that has started to occur recently when I boot peppermint 10 that is based on ubuntu 18.04 from a usb drive. The error 'system boot order not found- initializing default' shows briefly & then it boots into peppermint. Can you help me? I think it probably occurred after a kernel update & is to do with the grub boot? I've run peppermint from this usb drive since last year & not had this problem before. Thanks please be patient with me I'm new to forums - holdfast

[oldfred]

Moved to Other OS since not official flavor.

Did UEFI Secure Boot get turned on?'
Or default boot order changed to look for something that does not exist and then it changes to second alternative & boots that?

Lets see details, use ppa version with your live installer (2nd option) or any working install, not Boot-Repair ISO:
Please copy & paste the pastebin link to the Boot-info summary report ( do not post report), do not run the auto fix till reviewed.
https://help.ubuntu.com/community/Boot-Repair