How can we help?

The chuck might have debris in the jaws, which could make adjusting the chuck harder or stiff.

Open the chuck fully and clean out any build-up of dirt and dust - preferably with compressed air. 

This can be done by blowing compressed air (either from a can of compressed air or an air compressor) into the open chuck around the internal jaws until build up is removed. 

You can also use a small pipe cleaner (cylindrical brush) to clean the debris. 

You may need to cycle open and closed the chuck jaws to loosen all the debris.