Disclaimer I have never used face transfer except to fuck around around with it.
Its asymmetrical because its from a real face, the only thing I can suggest is the opposite of what I do, is use asymmetrical sliders to make symmetrical faces asymmetrical. Like move the sliders backwards, you may have to turn off limits.
Like this
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There are other ones, even search asymmetrical in DAZ and see if it has one by default.
Yeah exactly, it's because real faces are not symmetrical.
So if you're not OK with that then you could literally just go into the Face Transfer skins folder and photoshop the side you prefer over onto the other side.