9.3mauser may be onto something, here. This sounds more like an alignment problem. When you move the finger lever. Is it always in the same direction, that works?
Examine the projection on the lever. Are there any burrs, or scratches on it to indicate contact with the slot in the lower tang? As suggested, some gentle stoning and polishing of the lever projection may correct the problem. Does the projection(pin, if you like), line up squarely in its slot in the lower tang? If not, the safety lever is misaligned slightly...likely at a bit of an angle...,also causing it to bind. May only require loosening the screw and realigning the lever safety and spring. It is also possible that the projection is bent a bit. Or, the entire safety lever. Checking it on a flat surface will soon tell the tale. While you're at it, I'd also examine the pin holding the lever safety in place. Is it bent slightly? This might also cause the lever to catch a bit. The little bit of vibration from moving the finger lever may be enough to get it moving again. Hope some of this helps. Please do let us know how you make out.