Shimano 105 shifter problem

Hi, wondering if anyone can help me?

I have shimano 105 shifters on my 2 year old road bike. I've been having a problem with the left shifter. When I'm in the big front cog and shift down, the shifter works fine but when I try to change back up, the change occurs no problem but the down shift lever and little metal down shift trigger don't spring back inline and so I have to push them in manually to enable the next shift into the smaller cog.
ive attached a couple of photos as my explanation probably isn't very good.
the image show what it looks like after I've change up from the small front cog to the large.


any help would be massively appreciated :-)