Hi there - yes I have the same problem from time to time. Its mostly on the link room TV which is a BV6-22. I find its most often related to the Sky HD box where I get sound, but no picture. I find the only solution is to reset everything with a cold boot. It used to be worse pre 5.08, now it only happens every 2-3 months. Its HDMI related. B&O have no got good controller software for the HDMI implementation. Most of all their BS3/BV7 problems have been HDMI related. The other problem that also still rears its head is the HDCP issue. But again, a good reboot clears this up. I am confident your engineer won't be able to help too much as the its a software related issue unfortunately. You just need to raise with your dealer and B&O UK. I found them very helpful. Forget BeoCare - they don't.
I know B&O have a relationship with Microsoft, but the similarity of quality and QA between the two is uncanny. All testing is done in the field.
I'm curious as to what got fixed in the 6.11 release. Its strange how they go from 5.08 direct to 6.11.
Best, Mark.