Can't open write protected vault

Using OwnCloud, my local files are write-protected if i do not have write-access to a Folder.
Opening a fault on such a Folder Fails with error

11:27:38.993 [pool-3-thread-1] INFO o.c.common.settings.SettingsProvider - Settings saved to C:\Users\stolle\AppData\Roaming\Cryptomator\settings.json
11:27:45.613 [JavaFX Application Thread] ERROR o.c.ui.controllers.UnlockController - Unlock failed for technical reasons.
java.nio.file.AccessDeniedException: C:\temp\TestTresor\masterkey.cryptomator.bkup
at sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:83)
at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:97)
at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:102)
at sun.nio.fs.WindowsFileCopy.copy(WindowsFileCopy.java:165)
at sun.nio.fs.WindowsFileSystemProvider.copy(WindowsFileSystemProvider.java:278)
at java.nio.file.Files.copy(Files.java:1274)

It would be nice to be able to read such a write-protected vault.