From looking at today's movement on Flightradar it appears CDKA might be replacing one of the other S2000s.
CDKA operated LCY-DUS rotations today, CDEB operated the first IOM-LCY rotation but was then replaced by CERZ which had positioned DUS-IOM which resulted in both CDEB and CERZ being at Ronaldsway this morning.
CDKA may of course just be a lease for maintenance cover but I don't know if that is the case.
Hope the above helps.