hi David, thanks for your response, but that's not what's happening at all. Try it for yourself, and you'll see what I mean. The Godox trigger is two stage, half press and full press. Half press (according to the manual, page 32) should autofocus. Full press should open the shutter, and presumably fire the strobe. What actually happens, is that a half press fires the strobe - that's all it does. I can fire the strobe repeatedly with a series of half presses, and the camera doesn't autofocus or open the shutter. Full press focuses and opens the shutter, but it doesn't fire the strobe again.
My Yongnuo trigger does what I would expect. It first autofocuses, and when the camera has acquired focus, the shutter opens and the strobe fires.
I've since discovered that by mounting the XPRO-C on the hotshoe, and attaching a separate Yongnuo receiver to the sync port, I can use another Yongnuo as the remote. Problem is, the XPRO is now on the camera, which could potentially be on a tripod seven feet in the air, or several feet away from where I want to stand. The whole point of buying the XPRO was to be able to remotely control camera and strobes with a single hand held unit.