what is happening is that open-e writes a serial number on the disk to keep track of them
when you broke the raid 1 by removing the disk, the software was expecting a new disk drive to be added back to the raid

by adding the just removed drive you are confusing the software.


to keep you testing going, by reformat the drive so that there is nothing on it.
(I know there is no data but the serial number is there)
you can use the console utility in CRT-ALT-X "delete contants of unit"
this will wipe the drive clean.


also I think the software RAID does not support hot swap of the drives.
(at least it did not when I tested this )