Excellent. This is all I really needed to know. It's a bug in 4.5.10, gone in 5.0.3. I've done a test migration between those two versions on my test system and it went through without a problem. I'll pass this along and I'm sure the command line backup followed by a cold rsync will satisfy our requirement for roll-back and/or disaster recovery
Cheers,
James
PS - please mark as solved.