As to WD-40. When I had my gunshop in the late 70s I had a number of duck guns come in that weren't firing the second shot. The culprit was WD-40, hunters after a day of hunting would spray the stuff in the action or alongside the trigger and the stuff turned to a brown goo eventually thickening to where triggers didn't reset or fire. Mineral spirits cleaned them up for me then light sewing machine oil sparingly worked well.
I have a German commercial sewing machine that I converted to treadle. I left it at my mom's when I got divorced, my sister lubed it with WD-40 and kept using the stuff on it because it got harder and harder to use. After I brought it home it took years of cleaning to get that crap out of it.
