in short: whenever you did more than a few changes in ac or weapon or vehicles .xdp files and you are not sure that you deleted manually all the according bdp files to make the changes work. (eg. when modifying weapon loadouts or adding effects) Have used the zappers from time to time and they worked without problem, just your cfs needs a bit longer to load at the first start after you´ve used the zapper cause the programm has to write new bdps.
-- btw: nothing can beat a good BACKUP in case something goes wrong with modding
--
Please correct me folks, if this advice is wrong or incomplete.
Happy flying, Emile, yours wolfger