Procedural Mesh Materials get a weird split

Development Rendering
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1

I followed the Procedural Mesh wiki and have my mesh generating nicely, I set my UVs properly so the texture is orientated properly except I get this weird effect where one triangle of the mesh seems to have a bump a map where the other one doesn’t.

Here’s a screenshot:

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I’m using the M_CobbleStone_Rough material from the Starter Content in this pic.

2

Using a material that has nothing applied to Normal fixes this problem. I have no idea why.