I'm having a similar problem on my 600D. For me it doesn't make a difference whether the 2s-delay is enabled or disabled. What causes the problem for me is the duration I press the shutter. If I just press it very shortly, everything's working fine. But if I keep it pressed for several seconds (as you would do with the Canon-bracketing feature, I think), the first two frames of a 3-frame-HDR are exposed for the same time. So I for example get 1/80, 1/80, 1/320 instead of 1/80, 1/20, 1/320 for a +-2EV bracket.
Usually I would say, no big deal, just remember not to press the shutter too long. But I'm using this feature with the eMotimo TB3, where I can only set a static time (the time, where the system stays still) and not an exposure time additionally. So I have to set the static time long enough for the camera to finish the bracket, but during this time the shutter "stays pressed" by the TB3.
I also read a couple of times that people only had the problem when the camera was in another mode than M or when they had other shooting modes enabled than "single shot", but for me it really doesn't work with single shot and M mode.
If only someone would be able to clarify if this is a bug or if something is set up incorrectly.
Usually I would say, no big deal, just remember not to press the shutter too long. But I'm using this feature with the eMotimo TB3, where I can only set a static time (the time, where the system stays still) and not an exposure time additionally. So I have to set the static time long enough for the camera to finish the bracket, but during this time the shutter "stays pressed" by the TB3.
I also read a couple of times that people only had the problem when the camera was in another mode than M or when they had other shooting modes enabled than "single shot", but for me it really doesn't work with single shot and M mode.
If only someone would be able to clarify if this is a bug or if something is set up incorrectly.