pyramid - 2017-09-08

Strange behavior: When trying to auto-mount a previously mounted TrueCrypt volume with VeraCrypt on the same slot will briefly create the /media/veracryptN dir and the pop the error message "Auto-mount failed due to one or more of the following...".
When auto-mounting on a different, previously unused slot, mounting works fine.
The error persists through reboots.

# veracrypt --version
VeraCrypt 1.21
# uname -r
4.12.8-1-default
# cat /etc/os-release 
NAME="openSUSE Tumbleweed"
VERSION="20170823"

How can I check what causes this trouble?