Okay, I need to point this out, just because I hate it when people ruin machinery.
More machinery has been ruined by people mistaking WD-40 for a lubricant than I care to think about. And if May is making this mistake, it's no damn wonder her shoulder joint wore out. The personal lube, while not a terribly good machine oil because it evaporates too fast, is a much better choice mechanically speaking than WD-40 because it isn't actively harmful.
WD-40 IS NOT A LUBRICANT. It is a hygroscopic antioxidant. It penetrates rusted joints, helps loosen rust, and drives water off of surfaces where it's applied. On regular metal parts that's not actively harmful, and it can help free seized joints if they are seized due to rust. But you need to clean those parts thoroughly once you've got them free, and then follow it up with an actual lubricant.
But joints and gears in moving parts that are supposed to be long-lasting and low-maintenance are made with oil-impregnated bearing surfaces. On a microscopic level, oil-impregnated gears look kind of like swiss cheese only with the holes further apart. When they start getting a little warm, the oil inside them expands and goes between the bearing surfaces where it's needed, through microscopic pores in the surface of the metal. When they cool off the oil is drawn back inside. So they run for years and years with only very occasional oiling to replace the tiny amounts lost.
WD-40 gets into the microscopic pores and stops the self-lubricating action from working, and it's damned near impossible to get out. People who "lubricate" sewing machine gears for example with WD-40 doom their machines to an early death. People who repair sewing machines usually just replace all the gears if they learn that WD-40 has been used - if the machine has run for more than a few hours since it was used they'll be worn out, and if it hasn't, you'll still have to remove all the gears and put them in an oil bath with an ultrasonic agitator overnight to get them clean again and it's less trouble and faster to just replace them.
If you want to lubricate delicate machinery, or replenish self-lubricating gears, use kerosene or a very light machine oil. Marvel Mystery Oil is a great product.