Hi,
thanks for your explanation. The good news is that I can confirm that the odroid XU4 as well as the Raspberry Pi B are working without any problems (even after several reboots everything looks fine).
Just as a hint: in my case the sd-card reader is now available under /dev/mmcblk1 (and thus the first partition can be mounted by applying the mount command to /dev/mmcblk1p1. Before it was /dev/mmcblk0.
Best regards
P.S.: I will mark this thread as solved. (Unfortunately I had to change the subject because of limitations in the number of characters. )