draklive-install calls a umount_all() subroutine to ensure all disks/partitions that will be presented to the partitioning wizard are not currently mounted. But it only checks against mount points in /etc/fstab, so will not pick up disks/partitions that have been manually mounted or auto-mounted (e.g. by Thunar). The installer will then cheerfully allow you to delete those partitions, leading to the usual problem of getting out of sync with the kernel.
commit 4f6b3b5372ed0d5e1d0044a23d658dc8c5c4e9f9 Author: Martin Whitaker <mageia@...> Date: Sun Feb 12 11:33:41 2017 +0000 Ensure all selected devices are unmounted before partitioning (mga#20268). --- Commit Link: http://gitweb.mageia.org/software/draklive-install/commit/?id=4f6b3b5372ed0d5e1d0044a23d658dc8c5c4e9f9
Fixed in draklive-install 2.10.
Status: NEW => RESOLVEDResolution: (none) => FIXED