Mojave Migration Assistant Unable to Copy Documents, Pictures, Music

I was able to resolve this issue by rebooting my new MBP in recovery mode and doing a clean install of OS X after erasing the existing volume by using Disk Utility from recovery mode. The step of wiping everything out first is important or some files that doomed your previous attempts to migrate will be left behind to doom all future attempts.

The issue was that there ended up being two versions of my user account that got created when the initial migration happened. Migration Assistant crashed on me when running it from start-up the first time I powered on my new MBP and it behaved erratically from the start. Somehow a duplicate of my account got created and Migration Assistant ended up migrating to that duplicate account, which was not recogized as the owner of most of the documents that was on my old MBP so the files were either never moved or discarded immediately after they got moved.

One way you can tell if this might be happening to you is if Migration Assistant appears to stall for incredibly long periods of time. If the progress bar rarely moves and it says something like 18 hours remaining for an entire two hours, you are probably experiencing this issue. I have nearly 1TB of photos. None of those were moved so when it reached my photos stash, the progress bar froze for many hours. I presume what was happening was that Migration Assistant was trying to move that 1TB of files, failing a single file at a time and because no files got moved for hours, the progress bar never advanced and remained frozen at the state it was in when the last file was successfully moved.

If the progress bar freezes for 10 minutes or even 20 minutes, I wouldn't worry about it so long as it seems to be advancing at regular intervals and the freezes are the exception rather than the rule.

Another sign that you're suffering from this issue is if you browse a cloned copy of your old drive and you're unable to view the contents of the folders that aren't getting transferred. They'll have a red circle over them to indicate you don't have permission to view the contents and Finder will report that the folder is 0 bytes in size.

Everything that I described above is a sign that the new Mac isn't recognizing the user(s) of the new Mac as the same accounts that existed on the old one and you just need to wipe it all out and start over.

I did this transfer exercise four times in all. It took three full days! The fastest was a TB3 to TB3 between the two MBPs directly. That took about 8 hours, but it meant I couldn't get any work done on either computer in the time being. The slowest was hooking into a Time Machine volume over Ethernet which took 24 hours. I didn't try over WiFi. I'm sure that would have taken even longer.