I was able to reproduce the problem on the latest master and with this change it seems to be fixed.
The problem is that during the partitioning/formatting the umount_all_existing is called multiple times, even after existing partitions have been deleted already which results in trying to umount these deleted partitions as a old reference object is used.
There shouldn't be any need to call the umount each time a partitioning or formatting is performed but only once for each disk involved.
This fixes #2496
I was able to reproduce the problem on the latest master and with this change it seems to be fixed.
The problem is that during the partitioning/formatting the
umount_all_existing
is called multiple times, even after existing partitions have been deleted already which results in trying to umount these deleted partitions as a old reference object is used. There shouldn't be any need to call the umount each time a partitioning or formatting is performed but only once for each disk involved.