First of all, you should not use new boards with old software. I try to keep the current software compatible with old boards, but not vice versa. Please use the DRS.cpp library from the current V5 software, otherwise your time calibration will not work.
If you then do the calibration with the V5 software and the V5 board, you will see that the bin widhts of the DRS chips are not the same. Actually they are "oscillating" between ~130 ps and ~270 ps if you run at 5 GSPS. Some bins are even negative, this means that the next bin sees the signal before the previous bin. This is correct and due to the specific layout of the chip which is not perfect. Using the new time calibration with the current software, you should be able to make time measurements with a few ps accuracy.
I am setting up a new DRS4 rev5 but using drivers and software we were recently using with a Rev4 (with a recent release of the drs4 code, from mid-2014).
I am writing since I see peculiar behavior of the calibrated times when I read them back from the Rev 5. I get events where the first time returns 0 (which was always the case on my Rev 4), but the following time is negative -- this seems to be wrong since the times should always increase.
Is it a problem with my running the time calibration or a problem with the board itself? For the record, the integral nonlinearity displayed during time calibration "looks" very different when running with the same (recent) drsosc on the two boards. The rev5 has apparently a much larger amplitude.