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Shoot in Raw mode, even for in-camera HDR. Then you can examine the individual Raw exposures to see what they hold.
If you did or do shoot in Raw, you can take the constituent Raws and process them in Canon DPP's HDR modes. You'll be able to see how adjusting the parameters affects the images and how the different modes come out.
I am sure your camera is not at fault.
Still missing are whether it was a one shot "hdr" or a multiple exposure HDR.
Are you able to reproduce the effect? If you can, then it would be very interesting to see the source Raw or Raws, converted in DPP or PS or LR, converted straight in Standard mode or Faithful mode and resized for the web.