First, please carefully check on you report whether all parameters are identical.
Compare also the Loss diagrams.
If produced by different versions, you can look for eventual modifications on the historical evolution of the software in the help "Overview
> Historical evolution of the software
", or on our site http://www.pvsyst.com
/ Software development
Now if you start from Meteo data in monthly values, the synthetic hourly data file is constructed using a stochastic process: with 2 different executions you will have completely different years (sequences of days and or hours in a day). This may lead usually to discrepancies of the order 0.5 to 1% in the yearly result.
These are indeed unavoidable uncertainties due to the stochastic models used.
Therefore if you want to perform a quite identical simulations as a colleague, you have to share the exact hourly meteo file used (*.MET).