text.sourceText fontSize increment is anchored opposite of layer's Anchor Point

After some tests, it looks like a clamp method I've applied to my Text Layer's position property is causing the issue. When I disable the Position Expression, I get expected results. 

Still not a good thing that something happening in Layer>Transform>Position can affect the result. 
 

Thanks for filing. Hopefully, we'll hear back from the product team soon on this. Sorry for the frustration. Take care.

Cheers,
Kevin