that sure does sound frustrating!
How are you cleaning before fusing? Perhaps try something more
abrasive? such as pumice and water, or scotchbrite pad. check that
water “sheets off” fully.
What flux are you using? Though many brands work, my favorite is Rio
I find that when fusing and granulating, it is not enough to see the
surface melt— while using the torch, I watch EACH granule (well,
ALMOST every one) to see the fused joint between the two parts. Do
you do that?
If none of these thoughts helps, I would be willing to try to watch
you via Skype, or some other screen share, to see if I can spot the