I don't have a 970, but a 1070 and I have the same issue. I've noticed that it happens when I change between sources as well, i.e. going from a DVD (Dolby Digital/DTS) to a satellite program (one of the other Dolby Pro Logic modes).

I've also noticed that the unit will sometimes not recognize the "flag" of a different mode. That is, it will remain in a Pro Logic or some other mode when there is clearly a different source mode.

FYI-I have upgraded the firmware as well.