@tsukraw There's no need to uninstall the old version, the upgrade is enough.
The feature to disable time sync is also just a convenience shortcut for setting the TimeSyncMode value in HKLM\SYSTEM\CurrentControlSet\Services\xenagent to a DWORD of 0. You can set it manually or through Group Policy if you wish. (In fact, GPO might be a better solution on domain environments)
@nikade this is a good news : that will be easier to test and debug.
during an import you should have a nbdkit logs of ${diskPath} are in ${tmpDir} where diskPath is the datastore/diskname.vmdk and tmpDir is something like /tmp/xo-serverXXXX
the logs are in a stderr file in $tmpDir ( they can be quite big )