Cloned 8.1 will not boot on SSD

Hi, I have a new computer (UEFI) with a 500GB SSD (disk 1) configured as MBR on which Win 10 Home is installed and working.

I have reduced the partition on the SSD and created a new Win 8.1 install which also works fine as a multi boot using EasyBCD to configure which I have used for years without problems.

I have installed some old HDDs and copied/cloned a Win 8.1 partitition from disk 3 using EaseUS onto the SSD with the SSD box option ticked but am unable to boot to this partition which I specifically want to keep and, ultimately, I want to do away with my original Win 10 Home in preference to my various Pro licences. When selecting this partition on the multi-boot options, whether as default or selected, it always boots to the original partition on the HDD whilst the other options on the SSD and the HDDs (Incl other Win 8.1, 7 and 10) work fine.

I have been round and round in circles and I think I've tried all options and setups but it still refuses to boot the copied partition on the SSD.

At the moment, I have the UEFI configured in Legacy mode and I have Fast Boot disabled.

Also, at the moment, the boot menu is showing as a "DOS" list rather then the newer Windows GUI list which also didn't work previously. Not sure which setting I changed resulted in this change.

Any suggestions would be appreciated.