Try changing the callback from #filePostOpen to #filePostOpenProcess. I'm not sure that will work though. Would it be possible for you to upload the file? Autoback isn't usually a setting that is saved per file. You could also try a demo of a newer version of Max to see it still happens.
If this is the same problem I have all the time, then I have a fix for it. If you can go into the xref objects window and just click on the Update button and have the xrefs it couldn't find when you opened the file pop into place, then it's the same problem I have. Here's the fix... <font class="small">Code:</font><hr…