I distinctly recall that these flash quotes occurred after 2030 ET on Sunday, November 27 - and that is specific as I will get. The offer I am referring to was roughly in line with the market so that should narrow it down enough.
Granted quotes for all brokers in GBPUSD that I have access to were on the wider end. I do recall that EFX/MB Trading was not going as nuts as other brokers for most of the time.
HOWEVER, multiple times I did see the "no bid" flash quotes. I am absolutely confident in this as it happened many times. Once, I might not have believed what I was seeing. The spread difference between 1.9150 and 1.9412 odd > 260 pips.
So if one of your clients executes a market order to sell GBPUSD at market and then it flash quotes that "no bid" right then, I can see them on the line with your desk. "Well, you should not have used a market order...." That is exactly what I have been told by other brokers so definitively say that your desk would have busted such trades in that case.
If you track the stats of your markets you should be able to see it plain and clear... Or does your firm do zero tracking of the markets it offers? IT IS ONE OR THE OTHER. YOU EITHER SEE WHAT I AM TALKING ABOUT OR YOUR FIRM DOES NOT AUDIT THE MARKETS IT OFFERS.
BTW, any other clients see what I am talking about? Would like to know, because if not then that tells me a lot about your client base...