Old Steam Radiator not getting hot completely across.

Steam radiator was cold and valve was stuck in open position and was getting heat. Waited until cold, I was able to close all the way and re-open. Radiator now gets heat to about 1/5 of the width. Bent was replaced last year.

My other radiator in another room gets heat across complete with, so I suspect the valve maybe at fault since it did improve when I did the above.

Any possibility the vent or air trapped inside is what’s preventing it from getting hot across entire width or is it time to call professional and get valve replaced?