I have a 65 Mustang that got so I couldn't start it at times due to the ignition switch sticking. I shot WD-40 into it and flushed it out, and it worked like new. That was nearly 20 years ago! I use WD on everything that needs freed up, and have never had any negative consequences as you describe. I've also never seen even a hint of the "sticky film" you describe. After using WD literally thousands of times, there have been few (if any) times where I saw no improvement. I have a clock hanging on the wall in my garage that didn't work when I got it 7-8 years ago. Guess what I fixed it with...??
I'm thinking that with a 150 year old clock, who knows what all had happened to the interior workings. Kinda thinking it's problems may have started a long time before WD-40 was invented.
Ken & Jeannie
96 Vectra Grand Tour 35' DP
Jacey (terri-poo, waiting at the rainbow bridge), Jack (silky terrier)