Time Machine doesn't restore split disk reliably?

A few weeks ago I asked Time Machine to restore my iMac to its state a week earlier. (Restart, cmd-R, restart from Time Machine backup.) Everything appeared to come back OK except when I tried to start Windows it went to "Preparing Automatic Repair". After several minutes, it decided it wasn't able to repair the system. I tried restoring the entire Mac from a different date and then just the Windows pvm from other dates without getting it past Automatic Repair. During a remote session with Parallels Support, the tech. tried restoring the pvm from two different dates with the same result. When she restored it from a later backup date, Windows said it was repairing the disk and then completed startup and appeared to work OK. The tech. said either Windows wasn't working correctly at the time of the earlier backup(s) or Time Machine didn't do them correctly and closed the ticket. I've used Time Machine for quite a few years and never had a problem restoring the Mac files. And I use Windows most days and would have noticed if it was having such severe problems it couldn't start. (And then healed itself so restores of more recent backups work???) Being the skeptic I am, I've:
- Gone back to a single pvm file.
- Excluded it from Time Machine machine backups to avoid clogging the backup disk with pvm files.
- Made sure any Windows user data I care about is in "Shared Profile" folders so Time Machine backs it up with the rest of the Mac.
- Made sure I can rebuild Windows other than the user data from scratch if I lose the disk or just Windows.
(Actually, I maintain a secondary backup system for the Mac but that's a different story for paranoids.)

Has anyone else had trouble restoring a split disk pvm with Time Machine? If so, maybe we can persuade Parallels they need to look into it. Note that a successful restore doesn't necessarily mean all is well. It may just be that Windows didn't happen to be updating data across block boundaries when Time Machine read them or the restored image is actually corrupted but you haven't happened to try to run the code or noticed the bad data. Scary thought.