We are aware of the error with the Extract MC Hydrographs tool and it will be fixed in the next release of RORB.
The location you select in the “Select AEP and hydrographs for extraction” window is used to identify the representative event to export hydrographs for (e.g. an event representing an AEP of 1 in 100 at that location). Hydrographs will be exported at all other print nodes for that representative event (e.g. flows coinciding with the 1 in 100 at the location you specified).