kev, the reasons you asked would all be possibilities, except an incorrect ratio
Cure time for epoxy is heat dependent. A 10°C rise will cut the cure time in half. So applying epoxy in a very warm room will shorten the cure time, reducing the time for it to flow out and level.
Applying too much finish will cause a number of problems, and is the most likely cause of your issue.
Don’t mix until you are ready to apply. Curing starts as soon as the two parts are put together.
achieving a consistently fine finish is a matter of experience. Ask ten people to explain their procedure with finish epoxy, and will likely get ten different procedures. You need to find yours, and when you get a finished product that meets your standards, do it that way, whatever way it was, every time.
Regarding your problem child in the above pic, try to remember exactly what you did when finishing that rod. And do not do that again. I know, that sounds like a smart arsed comment, but that is exactly how I found my procedure. Making mistakes and not repeating them.