My suspicion, after enjoying several commercial custards, and despising most of them, as well as sampling more than a few flavor concentrate creams, custards, vanillas, milks, avocado, soy, rice, and anything else in that profile, is the vanilla, and some milk notes. They seem to have this acetone quality that, unless blended properly with similar notes, and smudged under other flavors, such as cinnamon, can be abrasive, and potentially repulsive, if the pallet isn't sufficiently fooled.
Have you tried rice milk custard? As a lactose free food? I would think that that would be, if made properly, quite delectable.
ETA:
@stratus.vaping it could also be settings related. These flavors generally require specific temperature range, so air flow and wattage could drastically alter things too. But if the knuckle test is replusive, then I doubt the vape would be better.