I used fast hardener with the usual Epoxy as its only a small piece and allowed for it to degas for 15 minutes after stirring it thoroughly. I ran the infusion through and made sure that the epoxy being pulled through the catch pot side came though for a good while so any aired epoxy was removed. 

can be many things in fact; leaks, to much peelply on that spot, to much infusionmesh, resin not stirred well enough, a spot close to the resin in-out, cold/heat, demould to early, did you use spraytack (did you use to much there?) is it a spraytack for composites or not?!