Often the cylinders can become clogged up inside with dust and dirt. First thing to do is stop using WD40, never use it on any cylinder, it mixes with dust etc and forms a sticky paste. To get the muck out use Carb Cleaner, you'll know it's working as the liquid coming out should be filthy. Follow that up with generous sprays of Silicone release spray and keep working the key in and out.
Once it's able to go fully home try turning it with LIGHT pressure and if it will not go keep on with the Silicone, if it will still not go after a couple of days a bit of heat will often work. These pics are of an H2 lock and you can see the heat melted the dirt/dust etc. once moistened with the Silicone spray.
Good Luck

