Problems with deck stain scuffing after application.

Hey everyone, I applied some Flood, semi transparent a few months ago when the weather was not quite so muggy (I live in Augusta, Ga) and I'm not too satisfied with the results. I applied 1 coat on the handrails and posts and I noticed after it had dried, that it was easily scuffed. In other words, simply scraping my fingernail across it would leave a pale, chalky scratch mark across the surface.  

I was told by the experts at PPG that I likely over applied and should've been wiping off the excess. So I did what they said and set up an experiment on a scrap board. I applied a single coat and wiped the excess off after a certain amount of time (30 seconds, 1 minute, 2 minute, etc.). After the 2 minute mark, the scuffing was much more evident.

However, now the stain was too light and required a second coat. I waited about 20 hours before applying the second coat, and wiped out off almost immediately. It probably only sat on the board for about 10-15 seconds. The color came out great. But now, it's back to scuffing again just as bad as the single coat, over application. FYI, these boards are all as dry as can be. They've been installed for over a year before receiving stain. There was no rain for at least 48 hours before our 48 hours after application. I'm just at a loss bc the color is perfect, but I don't want to have to worry about it looking scuffed from a dog walking across it or something like that. Does anyone know what might cause this?