hello bitbob,
i have the encore too , but i flashed it with the "BIOS Flashback" function (with the butten on the backside) over USB stick and i have no trouble with CSM mode on and off.
My TPM was already on by default and i am on UEFI boot on a SSD , no trouble here with BIOS 1101 on win10 , maybe Reflashing it over the USB BIOS Flashback funktion and then Directly "load optimized defaults" and after that "CLR CEMOS Button" and then configure it new. from other Rampage boards i know sometimes it flashes not corectly the first time , better is reset the BIOS and start new ...
Greetings