Bessa-L advance slip is common. The camera is not worth sending to a repair shop. Don't put in garbage. The problem is the tension on the take up spindle. Open the back and using a butane lighter, needle nose pliers and a paper clip. Heat the paper clip and melt a small hole near the top of the spindle and push the paper clip. The little bit of melted plastic puts pressure on the spindle and the shaft below. It works. Would not do on camera worth more than $50. I do not know how long it lasts but if it starts to slip again, out comes the butane lighter and paper clip. Sometimes the best fix on a plastic camera is to melt it a little. I will not be responsible for burnt fingers or homes set on fire.