Hi Nir -
in my case these VMs were migrated from VirtualBox to oVirt using some of the VMWare provided tool
and then virt-v2v to convert images. Here's the example of the meta file -
DOMAIN=92be9db3-eab4-47ed-9ee9-87b8616b7c8c
VOLTYPE=LEAF
CTIME=1529005629
MTIME=1529005629
IMAGE=f0d0b3b3-5a31-4c9f-b551-90586bf946a5
DISKTYPE=1
PUUID=00000000-0000-0000-0000-000000000000
LEGALITY=LEGAL
POOL_UUID=
SIZE=41943040
FORMAT=RAW
TYPE=SPARSE
DESCRIPTION=generated by virt-v2v 1.36.10rhel_7,release_6.el7_5.2,libvirt
EOF
These disks worked fine on 4.2.3.8 but I wasn't able to import them into 4.3.4.3 unless I changed DISKTYPE line manually.