Something I've done on more than one occation when I'm rushing is add the wrong ingrediant to something I'm mixing if my bench gets clutterd and I grab a can of something thats in the wrong spot.
The FIRST thing I start thinking about if theres a problem is what did "I" do wrong because in all the years I've been at this I cant think of one time it was one of the products being at fault it was always me. after you've mixed thousands of gal you start doing it without thinking and thats where you run into trouble. A clutterd up paint bench is my biggest reason for trouble ,I have to keep everything up on the shelf and only what I need on the bench,so when basing theres the base and the reducer on the bench ,thats it ,when I start the clear everything goes back up on the shelf and only the clear ,hardener and reducer is on the bench. being a bit of an air head can be a problem but you can learn to get around it.
99% of the time it'll be human error thats the culprit,in my case anyways...