I know that the behavior of your BIOS does not depend on what OS is installed but many people got the exact same problem after upgrading to Ubuntu 17.10.
https://askubuntu.com/questions/970451/unable-to-save-bios-options-after-ubuntu-17-10-upgrade
https://ubuntuforums.org/showthread.php?p=13714192&t=2378374#post13714192
Your bios DOES depend on the OS. Thats what UEFI means. It hands the BIOS settings over to the OS. Ubuntu 17 may require your mainboard bios to be SWITCHED to UEFI mode. I will check to see if thats true. In the meantime please STATE your mainboard, and its VERSION and its BIOS version as it may be too old for that ubuntu. *** UEFI mode might lock a BIOS from any changes unless its the OS thats changing it properly according to the UEFI rules.
The only reason that I can think is that Ubuntu has started some kind of a warm boot which keeps your computer from shutting down all the way in which case you can shut your computer down remove the battery if it's a laptop remove the ram reinstall it and then go immediately into BIOS and it will work one time before you go back to that warm boot business Windows 10 also has the same problem