— You can remove the signature on the .apk exported by XDK. I had the same issue updating a CSJ app after updating and repackaging it with XDK to add online game modes.
I did it by opening the .apk from XDK with winrar. Deleting the 'META-INF' folder.
Then going through the usual steps of sign / aligning with old old keystore files from previous builds....
I tried doing this with my game, updated to XDK apk, signed with the same key as the CJS game. It updated fine but it reset the saved data, I use WebStorage Local Variables to keep track of all the saved stats. Did you have this problem?
Funny thing also happen now, my device cannot install the CJS version of the game anymore, it just refuses, install fail. Even after I uninstall the current XDK version game first. Really strange.