I ran a registry back-up this morning to get you the log info you requested. The backup ran to a good completion I used both "Win Repair" and the "stand alone tweaking backup" . I looked at past try's and found the error you are looking for it was:
[1/4/2016 - 1:13:26 PM] Backing Up File: C:\Users\Administrator\ntuser.dat
[1/4/2016 - 1:13:26 PM] Result: Failed - Error: -1 (API Reg Save Failed (), Tried File Copy, File In use, Cannot copy.)
[1/4/2016 - 1:13:26 PM] Backing Up File: C:\Users\Arnold\AppData\Local\Microsoft\Windows\UsrClass.dat
[1/4/2016 - 1:13:26 PM] Result: Successful (3.64 MB) - C:\RegBackup\ARNOLD-PC\1.4.2016_1.13.24-PM\C\Users\Arnold\AppData\Local\Microsoft\Windows\UsrClass.dat
[1/4/2016 - 1:13:26 PM] Backing Up File: C:\Users\Arnold\ntuser.dat
[1/4/2016 - 1:13:26 PM] Result: Successful (5.26 MB) - C:\RegBackup\ARNOLD-PC\1.4.2016_1.13.24-PM\C\Users\Arnold\ntuser.dat
I was running the backups from my Win session and not fm "safe mode", also this same error was reported by the "Win Repair" and the "stand alone tweaking backup"