Sticky lock cylinder on rear hatch

[RkyMtHgh]

Has anyone else experienced a sticky lock cylinder on the rear hatch? I've noticed that when I insert my key into the hatch's keyhole and turn it, there's a lot of resistance- almost like the cylinder is coated with a really viscous syrup or something. If I let go of the key, it won't spring back to its original position and stays stuck unless I slowly twist it back to the vertical position manually.

Any idea what it could be? Solutions? Thanks guys!