Thanks for upgrading to v6, and glad you like the 'All Pistons Next' function.
It's correct that in v5 the stepper's current and cued frame numbers were not reset to zero when loading a different combination set, whereas in v6 they are reset, since that was felt to be the more useful behaviour (given that we wouldn't expect people normally to be loading different combination sets whilst in the middle of actually playing a piece, and also given that when switching to a different combination set people wouldn't usually want to start from the same frame number that they were using last within whatever combination set was loaded previously). The changed v6 behaviour was also something that people had requested previously. This is the relevant entry from the v6 changes section in the release notice:
When loading a combination set the stepper cued and current frame numbers, the master crescendo, the last-used/lit master general (if any) and last-used master combination states sent via LCD panels and the MIDI console status output system, are all now reset.
There isn't an option for *not* resetting those things, I'm afraid.
I would recommend either:
a) Use the stepper's new editor functionality to copy all the relevant frames for the relevant piece of music into a single (e.g. new) combination set, putting them into sequence, thus avoiding the need to switch combination sets whilst actually playing the piece. Or:
b) Use the stepper's editor functionality to move/copy all of the relevant frames in each combination sets so that they start from zero (either in the same combination set, if the lower-numbered frames are all blank, otherwise into a new combination set).
(In v6 you can copy blocks of frames between combination sets.)
In general, my advice would be to avoid switching combination sets whilst actually in the middle of playing a piece anyway, since loading a large combination set could take a few moments, and potentially lead to things becoming sluggish whilst that happens (e.g. perhaps delaying MIDI notes slightly).