It's just rushing product, that's probably the only issue, and if you mixed at 1:1 and did 3 coats and tried to paint the next day. That is where the issue comes from, that is to quick to topcoat over the epoxy. This is a situation where I would wait 3 weeks. Is that excessive? probably, however it's safer. I would rather wait 3 weeks that wrestle it for 3 weeks. At least if I wait I can work on something else while it is curing. lol. Keep in mind if I use 3 coats i'm using it as a filling primer at that point, typically in replacement of a 2k primer.. For what you were doing a 2k primer would have been more efficient.
I also find ZERO purpose in applying 3 coats of anything unless the plan is to sand the majority off. My theory is that if you are putting 3 coats of something on you should sand the majority back off, if you are not sanding it off, what have you achieved? 3 coats is a fair amount of millage and when blocking that off you can fix imperfections, and also level out the surface, if you left three coats on you are just increasing the mill thickness. And I always feel thinner is better.