I used to get that occasionally. I think it is because, the open "command" can is also used to stop the boot mid-way from opening. That is, using any of the boot opening methods, once the boot opening has started, you can stop it from opening any further by hitting the open button again. Maybe the car is mis-detecting the key press.
If it happens to you every time (or very frequently), then take it back to the dealer as that clearly isn't correct. However if it is just occasionally, then maybe it is just "one of those things". You'll have to decide if it happens frequently enough for it to be wrong. For me, it would happen every now and then, which I didn't mind. However if it happened regularly, I think I would have taken it into the dealer to be looked at.
