Migration assistant destroys source drive

[Bjojade]

I've had this happen twice now. Migration assistant from a working machine to a new machine running Catalina. The migration goes for a bit, but then hangs up. Wait a day, and nothing progresses, so restart the unit. Machine reboots, but can't migrate from the drive. Plug the drive into another machine and find that the only thing remaining on the drive is a System folder with a boot.efi file. Everything else is wiped out!!!

I've never seen anything so destructive happening using migration assistant!! What's happening?

 

[Riwam]

It might help readers to understand your problem if you indicate clearly what MacOS was running in the source computer and which one in the target computer.
You speak of Catalina but not indicate in which of the two computers it was installed and what was running in the other one.

 

[Bjojade]

Sure, I can give a little more info. I have now had this happen twice in the last week. The first time it happened, I was migrating from a MacBook Air. The source machine was running 10.15 and working just fine. I put the machine into target disk mode and connected to the new MacBook Air via a known working Apple Thunderbolt cable and Apple Thunderbolt to USB-C adaptor. The migration started as normal, and everything looked like it would work. However, at some point, it simply stopped transferring data. The new machine was un-responsive. So, I restarted the new machine, but at this point, the old machine was destroyed and would no longer boot on its own, or be recognized as a source for data migration.

The 2nd time it happened, I was migrating from an older 2008 iMac. I removed the hard drive from the machine and put it into a known good SATA to USB carrier. Same thing. The migration started just fine, but then stopped. I left it over the weekend, but there was no progress, so I rebooted. Again, the destination machine pretends that nothing transferred, and the source machine is now wiped.