Centos 7 and Windows 10 Dual Boot Grub Not Saving Last Choice

I have a dual boot system with CentOS 7 and Win10. My install was totally vanilla (CentOS then Win10) and went fine. Everything is great except that grub does not appear to save my "last" choice from the boot load menu. I dug through all the grub configuration files (e.g. /boot/efi/EFI/centos/grub.cfg) and all the code seems there for recording the last choice. My /etc/default/grub shows: GRUB_TIMEOUT=5 ... GRUB_DEFAULT=saved ... GRUB_SAVEDEFAULT=true Is there anything obvious I am missing or need to do to enable this? My /etc/efi/EFI/centos/grubenv never apperas to record the latest selection. It always has: saved_entry=CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core) ##########[...snip...padding to 1k] I can't see this file from a Windows boot, but I did test via the "rescue Centos entry". I manually set the value in grubenv to Windows Boot Manager (on /dev/sda2) (the Windows entry) and this works out okay. However, booting back into CentOS fails to change it. It just seems I am missing something to enable this "save the last choice" behavior. Any ideas?