Since three different epoxies are having the same failure, I would rule out an epoxy issue.
That leaves you with three possible issues: not enough epoxy used per shaft, poor shaft tip prep, poor hosel prep.
Shaft and hosel should be cleaned of all previous residue using solvents and brushes, then they should be cleaned of all dust. I use isopropol alcohol, but denatured alcohol works as well. If there is a lot of play when shaft is in the hosel, use shafting beads or a shim if putting a .355 shaft into a .370 hosel. A collard ferrule can also help center a shaft if the hosel accepts them.
Does this happen with all the heads or just one or two ? If one or two, are they the same heads each time ?
The only time it has happened to me was a club hosel that was way to smooth and shiny inside. I roughed it up a bit with a stainless steel brush and it never came loose again.