Hi,
Thanks for your efforts. As stated the log is from a session where I manually killed the Dracut process. Without manual intervention the Converter fails with generic timeout.
The timeout has happened without exception with our servers that run the 3.10.0-957.5.1 kernel, although I tend to kill dracut now manually after waiting for 10 minutes or so (after maybe five times waiting for the 30min/1h timeout in the past).
However all these servers have been updated from previous versions of CentOS/RHEL. Perhaps there is something left from previous versions that intervenes current one and creates problems for Dracut. A library perhaps... Manually the same dracut command works fine with the converted machine's disks when booted from a recent CentOS/RHEL DVD rescue chroot.
If you are interested to investigate further, you could try to install 7.5 and then update it to 7.6 and try to convert that.
Terveisin,
-Tom