I was watching today as one of these bets came up.
An initial bet for £1 @ 1.04 gets placed, but then after that there is nothing - with an error message in the log.
I have "Allow small bets" set ON in settings, along with "Post small bets in one batch"; is it possible that the latter is causing the bet adjustment to be sent at the same time as the initial bet, and that is causing an invalid bet?