Camera model SL620. Lens cover does not automatically fully retract. A small portion blocks the top and bottom of the lens but will retract if touched. Tried blowing dry air on the cover and wiping with a soft cloth.

Apparently the lens has had some kind of impact to cause the lens cover to be bent a little. What happens is that the lens cover holder , or ring, on the end becomes bent or misshaped to a degree. This then causes a binding effect on the diaphragm assembly.
What I have done is to very carefully (while using good magnification) pry up on the edges of the lens cover metal edging on the inside edges. This will release the pressure on the lens cover diaphragms.
But, be advised that this is can harm the lens cover more, unless you are extremely cautious. That means to use a small screwdriver or some such tool to pry up on the inside edges carefully.
Also be advised that too much pressure can cause the whole ring which holds the diaphragm assembly together can pop up and off. Then the whole assembly can come apart, and that is very hard and can be tedious to put back together.