ML 2.3 on 50D, Long press shutter release issue, bug or design?

[MARKSE]

Hi, I've just started using ML on my 50D. What a great bit of software!  I'm shooting pano with 7 brackets with a wireless remote and found a repeatable issue. I'm wondering if this is a bug or the way it's supposed to work?

With the built in Canon -/0/+ three bracket shots I have to hold the release until at least the third exposure has started.

With ML a long press like this doesn't get the results. If I do a very short press of my shutter remote the camera clicks away and takes the 7 shots. If I do a longer press it takes just 1 exposure and stops. But importantly the exposure indicator on the LCD shows it jumping up and down to the correct exposure values, it just doesn't take the shots.