Park Glueless patch issue

[SteveV0983]

I have been using Park glueless patches for years and have never had one not stick. Until today. And I had never used the sandpaper. Until today. So I got a flat, found the little puncture, and for some reason unbeknownst to me, I did the light sanding today that they recommend and then applied the patch, pumped up, and went on my way. About 10 minutes later, it was flat again so I took it off and it turns out that the are that I sanded, which was a thin strip along the length of the tube, did not hold the patch. The areas that I did not sand were fine. So I figured I’ll just add an additional patch to either end of the original and that will seal it up – except I only had one left. Needless to say, it didn’t work.
Has anyone found that actually sanding the tube makes the patch not stick? As I mentioned, years of no sanding and years of no problems. Maybe I should have wiped the sanded area with a wet fingertip or something. Lesson learned I guess.