Hey Themeco,
in my latest Pro projects with child theme setup QueryMonitor tells me there is a missing dependency for x-theme in the pro-child/style.css. See screenshot below.
The page does not make any problems, so I don’t think it is a major problem. But the red QueryMonitor flag nags my developer heart (if you know what I mean ;).
I’m running Pro 6.4.19 and downloaded the Pro child theme today.
I think this is something you have to fix on your side?