Yesterday I upgraded Nexus 5 with OTA update from 5.1.1 to 6.0.
After upgrade when I started my applications build with B4A I noticed that the apps started as if after install.
I checked other applications and they kept their settngs.
I keep my data in the sqlite databases in the File.DirInternal sub-folder and it looks that the files from File.DirInternal were clean-up while upgrade.
Sure it is standard place.
So there are 2 options:
1) Bug of the Google upgrade process
2) I didn't consider something and this something brought to the issue.
I am trying to collect more information to sort out.