stuck morse lever

[maelduin]

I have an old morse trans shifter that is nearly impossible to move from one position to another. I have taken it out and partially apart, noticing that the lever cam has what looks like a ball bearing that sits in one of three detents. The ball moves if I pry on it pretty hard but the lever doesn't want to move. Is it only corrosion between the shaft and housing or is there something else I can't see? Getting that ball bearing back looks like it could be a real hassle.
Any advice is greatly appreciated. Thank you.