550D HDR issue?

[du3z]

Is this a known bug?

I'm using the following: 550D, ML 2.3.

I was using 3 brackets HDR in ML. For example, 1/40 at EV 0.

It will shoot 1/40, 1/80, and then 1/40 again!!
The following shoots will then start with 1/20 i believe, sometimes 1/40 - random.

Looks like I need to do a reshoot =( It's quite a nightmare when doing HDR 360 Panorama