I can confirm this also happens on our system with a very similar setup.
I believe that this is a duplicate of https://bugs.launchpad.net/ubuntu/+source/partman-lvm/+bug/108935
I can confirm this also happens on our system with a very similar setup.
I believe that this is a duplicate of https:/ /bugs.launchpad .net/ubuntu/ +source/ partman- lvm/+bug/ 108935