joshua:
You are suggesting, I think, that I may 'limp wristing' the gun. It occurred to me, briefly, but this type of failure is not indicitive of 'limp-wrist', and, having been shooting 10mm for over 20 years and not had the dreaded 'limp-wrist' I don't think it's the issue.
What is the issue, and you touched on it, is that the slide is moving fast. A stiffer recoild spring didn't really help, but I know what the problem is, viz., that the slide hits the frame so hard that the small spring which holds the slide stop in place is failing to hold it, and it lifts and locks the slide. EAA changed that spring, but it didn't help much (it did help a little).
I just need to decide if I want to send it back again and tell them what to do and deal with their gunsmiths and customer service, which are hit and miss; have it done locally - by whom I have no idea, try it myself, or leave it. It is one of the downsides of this gun - who is going to work on it?
Still, the ergonomics are great - I just love the feel of the Witness, and I'll probably just keep the full sized slide on the compact frame for now.
Tom