Hi,
Hope nobody minds me offering an answer to this. You will notice in-running that the lay prices will often lag well behind the back prices, even though the back prices are being met. In test mode, your lay bets will only be matched if the lay prices catch up and and you can actually see the amount being traded at the required price if you have the price ladder open.
The back price may bounce in very low for a second, but if it doesn't stay there then your lay bet probably won't be simulated as matched
In live betting in-running, you may well get matched without actually seeing the trade at all on the price ladder if it gets swamped with a torrent of bets and the both prices drop quickly.
Think I am right on this, and hope it helps
Larp