Quoted from MarkG:After cleaning the socket, soldering the barrel to the base often helps too (see http://www.pinrepair.com/restore/index3.htm#lites). It'll be much easier if both parts are clean an shiny, wiped with some solder flux and soldered with a good (e.g. 100+ watt) soldering iron.
/Mark
I do what Mark suggests, using a soldering gun for lots of heat and quickly getting the job done. I would also clean them off with some CLR since you have a lot of oxidation on yours. It’s always a trade off between how much you want to disassemble or rework vs. cleaning up what you’ve already got 
Dave
