Missing data

[Drum1]

Preview contains all the information in my file, but when I actually open the file 90% of it is missing. Autodesk showed how using the merge command brings the data back in a new file, which is fine; but it keeps on happening, and is a pain to remedy. Anyone know how to stop this happening?

 

[Len Rafuse]

Preview is just a bit map image made when it saves. If the file is
corrupted, the BMP may still look OK.

Are you just saving in SKF format and reopening and stuff is missing?
What version are you using?