Did you try to do your settings through the Console mode , by using an SSH software as putty ?
you can connect by using username : cli and password use what you put it in SSH software password option).
try to press CTRL+ALT+W , or CTRL+ALT+X and make your changes from there.
also you can press F1 for shortcuts help.

Also you said "When I remove one of the disks from the machine and boot it up...." and you are using RAID0 OR RAID1 , and both of this RAIDs must use 2 HDD at least!

so your array are done with 2 HDD, and when you remove one , then you destroy the architecture that RAID work with ( as I know),
so it’s not an Open-E error because you are doing something fully unexpected ! or am I wrong?
it’s like someone try to run computer without RAM or CPU