Have you ever used WD40 on something and had bad results ? Please share.

I don't know if this counts or not....

I was cleaning the rail part of the sliding glass door cuz it was getting harder and harder to open and close. I took the vacuum hose to it and even a screw driver to get in the nooks and crannies. It worked for a day then it started sticking again. So brilliant me took some WD40 and sprayed some on the railing. BOY did it start sliding! Sliding TOO well! We adjusted to it being able to open with just your pinkie finger but like most good things, it can not last. A week or two later it began sticking again so I went to clean the rail again and it was BLACK GUNK! It was thick and sticky. Not like syrup but like.... Gunk. It was so difficult to clean off the railing. I chiseled it off with the screw driver!