Gamma ray spectra gain match

I have a gamma spectrum corresponding to 16 Ge detectors. The data is in approximately 300 root files (run by run). I am sorting this data using TProof in batch mode. During the experiment, there is a shift in the peak for different detectors and different runs also. For example, if we consider the background peak for 208Tl, it should be at 2614 keV. But it is shifted in all the root files. I want this peak to be exactly at 2614 keV for all the detectors run by run. Kindly help me with this.

My first though would be that the shift is in the data themselves. I do not think TProof has anything to do with that shift. Just in case can you inspect one of the faulty files outside TProof and see if that shift is still present ? Very likely the data you stored in the tree (at tree filling time) are already shifted. In that case you should inspect/debug the program doing that fill.