Heat
It may be the viscosity of your epoxy, you might think of using some of the reccomended reducer for that particular brand for the first coat to thin it some. The use of heat has been used forever in custom rod building and I always reduce my first coat on the rods I build to reduce the likelihood of trapped air bubbles in the threads and too obtain deeper penetration. One final comment I was trained to always do a final wipe down prior to finishing with denatured alcohol as it evaporates quickly and does not leave behind any residue that some other solvents may.
It may be time too switch to another epoxy and see if that cures the problem..
It may be the viscosity of your epoxy, you might think of using some of the reccomended reducer for that particular brand for the first coat to thin it some. The use of heat has been used forever in custom rod building and I always reduce my first coat on the rods I build to reduce the likelihood of trapped air bubbles in the threads and too obtain deeper penetration. One final comment I was trained to always do a final wipe down prior to finishing with denatured alcohol as it evaporates quickly and does not leave behind any residue that some other solvents may.
It may be time too switch to another epoxy and see if that cures the problem..