Hello smern, hey, I had that happen once and it was the two part finish that was to blame. Try this, mix some up as you always would and 'finish' an area on a clean piece of glass. If you get the 'bumpies' you'll prolly want to get new Flex Coat. I have more info on this if needed but let me know if the problem still exists when you apply your finish to a piece of glass. Hope this helps !
Cheers,
MontanaMoose