Changing destination fails with "tmutil returned 11520"

[owahlberg]

I use ControlPlane and Tedium to switch between destinations based on location.
Sometimes when I try to switch to the time machine destination using Tedium it fails with an unclear error.
"Failed to change backup destination - Unknown error occured, tmutil returned 11520"

I have not found any additional useful information in the logfiles (see below), and manually attaching the drive and using tmutil setdestination + startbackup works just fine with no errors.

Any suggestions, or way I can get more information out of Tedium to pinpoint which tmutil command is failing?

This is what I got in system.log

Apr 30 10:03:46 dino.local Tedium[24094]: calling helper tool with SetDestination
Apr 30 10:03:46 dino.local com.apple.SecurityServer[15]: Succeeded authorizing right 'com.dustinrue.Tedium.SetDestinationCommandRight' by client '/Applications/Tedium.app' [24094] for authorization created by '/Applications/Tedium.app' 24094
Apr 30 10:03:46 dino.local com.apple.SecurityServer[15]: Succeeded authorizing right 'com.dustinrue.Tedium.SetDestinationCommandRight' by client '/Library/PrivilegedHelperTools/com.dustinrue.Tedium' [24213] for authorization created by '/Applications/Tedium.app' 24094
Apr 30 10:03:46 dino.local Tedium[24094]: call to helper tool succeeded, helper tool returned: 0
Apr 30 10:03:46 dino.local Tedium[24094]: command returned 11520