Posting a support request here. I read the manual and checked that all the plugins are updated.
I tried a custom custombackup.xml (below) as well as the original one.
There might be some bits in finnish, so ask me if you need help with them. Here's one line I found:
Tiedostoa tai kokoonpanoa CustomBackupLocations, Version=2.2.1.0, Culture=neutral, PublicKeyToken=null tai jotakin sen riippuvuutta ei voi ladata. Määritettyä tiedostoa ei löydy.
In english: A file or composition custombackuplocations... ...or some of its dependencies can not be loaded. specified file was not found.
CustomBackup.xml
CustomBackupLocations.ini
RagePluginHook.log