Real hard to tell what could be the problem. It could be gummed up with powder, carbon and dried up oil and needs a good cleaning...or something could be broken or bent in the action.
The 59a is more complicated in action than it had to be. I would remove it from the stock and have a good look around for the problem. If it's just dirty and you aren't comfortable doing a disassemble you could use some spray gun cleaner or a NON-chlorinated
brake cleaner with the little spray tube attachment while it's out of the stock to get in there and clean it. Follow that with some spray gun oil.
The bolt can be removed by removing the "bolt stop screw" that is located on the left, near the center of the receiver. Remove it, bolt slides right out.
This link might be of some help to you for a picture and parts you may need.