Could be for loco maintenance reasons. KK has been part of an LSA between Ajanta, Devagiri and Sachkand expresses at MMR for sometime ( The LSA arrangement may have changed, not sure on this one). So the GTL locos that have been working on the HYB-MMR sector for a few days will be sent to GTL with KK and the fresh set of Alcos that KK gets at GTL will start working as part of the LSA. Most likely the loco change will only be for the SBC bound KK and not for the NDLS bound one.
This is like Kerala express which gets an ED WAP4, which is due for maintenance, from Ernakulam, and switches to a freshly...
more... maintained WAP4 at Erode after a loco change.