Unfortunately I found two bugs within the first minute or so:
I got a sample document through private email. The first problem is that the chapter number of a child document will be 0 if the child document uses a different layout from the master document. Because lyx explicitly requires that master and child documents use the same layout, I guess this bug is a WONTFIX. I was not able to reproduce the reported crash, with open/close child documents, plus some simple editions. Still trying. Cheers, Bo