Comment # 1 on bug 1130431 from Arvin Schnell

From the logs:

LuksImpl.cc:80 THROW:  Luks bigger than parent BlkDevice

This looks like a duplicate of bug #1101870 and fixed already. But for
Leap there is not installer self-update so you will have to wait for
Leap 15.1.

*** This bug has been marked as a duplicate of bug 1101870 ***