Perfect transmute only giving suffix

While trying to find good bases for crafting a crossbow I've noticed that every time I've used a perfect orb of transmutation on a crossbow (been testing on gemini and siege, ilvl 78-81) I have gotten only suffix modifiers.
This has been consistent for ~40 attempts. Now this could be a conincidence, but that would be a 1 in 2^40 chance, roughly (9.09*10^-11)% or 0.0000000000909% chance (give or take a few multiples of two for not counting exactly how many I used). Also assuming it's supposed to be 50% chance to hit prefix/suffix.