Get a permit for a Tuesday, fixes half the crowds.

Four years with no problems is not luck, that is a pretty good run. WD-40 is mostly a solvent with a little oil in it, so yeah it flushes out the old gunk and leaves a thin coat that keeps things moving for a while. The catch is that thin coat does not last, especially in rain, so you end up spraying more often, which honestly is fine if you are the type to hit the chain every week anyway. Most people who swear by it are doing exactly that, reapplying all the time, so the chain never dries out. Your chain started skipping because you went four years without doing the math on wear, not because the spray itself was evil.

My brother in law did the same thing on his back door years ago and I swear he spent every October up on a ladder with a caulk gun muttering to himself. Thing is, the recessed look is so much cleaner that you forget about the maintenance until that first cold snap rolls in and you feel a draft on your ankles. He ended up putting a small storm door over it just to stop the wind from getting at the seal. Sometimes the pretty choice costs you a Saturday every fall. At least you know what you're getting into now.