Upon opening an unzipped assembly, which was pack-and-go'd in SW 2015, in SW 2017, parts of the assembly appear in strange places.  The "open summary report" lists a bunch of files that it is unable to locate.  According to the modeler, these missing files are not needed.  The extracted assembly has been opened on a "virgin" computer with SW2015, and there were no problems with erroneous placement of parts.