Grub 2:2.06.r322.gd9b4638c5-1 won't boot and goes straight to the BIOS after update

I’m still struggling with boot issues after the last grub update.
After doing almost everything written in the post I still can not boot my machine normally.
What I did before:
Booted with live USB, installed grub (as root), changed boot sequence with efi-bootmgr -o, etc, as descibed here.
Result: Now I can boot using the boot manager (by pressing F12) but not normally, where I get the error message “symbol ‘grub_debug-malloc’ not found”.
I also tried to enter the ‘Inside H20 Setup Utility’ (by pressing F2). All seems to be OK, expect of the Boot menu: there is just ONE entry: “2.”. (No HDD or USB entries)
Is there anybody out there who has detected similar behavior?
Is there a solution for this?
Thank you!
László
(If it’s not the right place, please give me an advise!)