The stack trace decoding depends on the availability of the map file produced during the SmartAssembly build. To retain map files indefinitely, you must use the mark as released
button on the post-build screen. If you do not do this, map files are still retained for 15 days, so the problem must be that the map file could not be found.
If you are using SA on multiple computers, you should put the map files on a network share, otherwise they are only available on the machine on which the build was done. To configure a network share for map files, please see the help