The Seemly Random Generator (SRG) is used for this mod, which means many objects are already used by vanilla DayZ SA. If you don't use a fresh installation of DayZ SA, some things will not work correctly! That's why there is an APK instead of just modifying your central building. It's safer and more convenient, so no worries! :) Don't forget to delete the map data file under Android/data/com.studio.dayzsurvivor2 if you want to recover some space on your device after installing WSM (just in case). Delete it at your own risk, and it will regenerate when you launch the game.