That is a good question. Through "experience", I wonder if you mixed the epoxy well enough? I did a bone head thing once where I poured the epoxy components together, screwed the lids on the bottles...then forgot to stir it up. Some dried, other areas remained tacky. That was all I could figure out...and I felt pretty silly...to say the least.

I use Threadmaster and have had no problems when I follow the instructions. One thing that I do is to warm the resin about 20 seconds, so it is easier to suck into the syringe and measure.

Food for thought......George