I've recently had some issues with lens adapters where the mount between the adapter and the lens is quite loose because the bayonet tabs do not have proper spring loading. This has been quite annoying as the torque required to turn the focus ring is enough to move the lens within the mount which makes fine focus adjustments a pain. Using a "precision engineering solution" I managed to (temporarily at least) fix the problem on my m4/3-to-EF and EF-OM adapters. As shown in the photo below the bayonet tabs are scored to create a rudimentary spring effect. If you get a small flathead watchmakers screwdriver you can insert it into the gap and open it up just a tiny bit. This is enough to get it to hold the lens in place without any free play. The metal used in the cheap adapters is not great quality and is quite soft and I suspect it will return to it's former state before too long and need to be opened up again. The soft metal also means if you are a bit rough with the screwdriver you may end up with some tiny metal shavings that will float around inside the adapter and may get inside your camera body or lens. I've noticed that even when you get a brand new adapter you need to check that it has been deburred correctly and there are no fine filaments of metal left that may come off.