Ok well, we have eliminated one thing at a time. All that’s left is your opacity mask and your model.
First of. The model.
Theres no need to have it be cut like your image shows above. Even if you plant to simulate physics on it later on, chances are you’d never notice the difference between a square mesh and a mesh with the 2 or 3 extra cuts at the tip.
So I would suggest you start with that.
cut, and re-map the UVs for one plank to be flat, so you can test it.
Second, the opacity map and the material.
assuming that the flat plank shows the same dark halo, then something must be leaking from the opacity mask into the material albedo.
how are you applying this mask to the material?
It should really just be used as an alpha over the lerp of the regular opacity and 0 (transparent area).
Last and bonus. For rendering the splintered part at the edge with the flat planks, you can use parallax on your material.
you could also fake the depth with double sided sheets that each have a different opacity mask mapped to them but that may get more expensive in the long run