Going back to the Sten, a few things I would like to add for information is:
The Sten MKI and II's also had a bad habbit of firing on their own without the soldier's finger on the trigger, due to the basic spring bolt used in them. I can not remember if they ever bothered to fix this in the later versions.
Another problem with the Sten was that many soldiers complained about the sights being pretty crappy (see below image)
Later on with the MKV version, they added the front sights of the Lee Enfield rifle to help improve aiming (See Below Image)
But the MKV had a few problems of it's own. The MKV was originally designed as a Paratrooper's SMG, but many Paratroopers complained about the forward handgrip being too weak and easy to break off during their jumps or landings. Some just broke them off on purpose.
It was a very cheap and very effective SMG for the British and Canadian forces of WWII, however it was far from perfect.
I always liked it though.