Is because that title is a lie!
Let me explain why.
Using task scheduler to convert workgroup PDM files works great for any files that can be opened "fully" in Solidworks.
Where it totally fails is when you have a large file with lots of features, an assembly or configurations that take longer than 9 seconds to "fully " open.
No matter what you do, even with time-out option this error still remains.
Here is the issue in detail that will trip you up if you use revision control.
Updating the vault keeps the files as they were, just updated, if they update..........
If you need to check-out a file for the above failure reason, then you need to copy any note that you have.
Rebuild the file, then on check-in re-apply that note if keeping the same revision.
If you use a revision table and do not re-apply that note, the original note is wiped off the revision table, leaving the note area blank with just the original date!
This also means that any document above this will need rebuilding.