I've just released a game on the google play store. Due to launch I've just detected 2 small bugs, with an icon resolution and an ad in portrait mode instead of landscape. That is the only 2 changes I made for the game and then change the version and export it with Signed Realease APK, for testing.
I did not change any other things or export option or key or whatever.
So I think the problem is due to R197 which was deployed between the two updates.