Having issues removing a heightfield pattern from a closed polysurface

I’m trying to make an engagement ring with a fern pattern subtracted from the base material. I’ve successfully managed to flow the pattern around the outer curve of the ring, but when I attempt to remove the material it always fails.

Both the base material, and the pattern are closed polysurfaces. I’ve tried boolean operations, as well as CreateSolid. I’ve tried to extrude the heightfield first as well. I’m just out of idea’s. The pattern is quite complex too so every operation I try takes a few minutes. I’m not sure if it is just the complexity of the heightfield that is creating problems or i’m just doing it fundamentally wrong…

The frustrating part is that I’ve done it successfully once before:

But now I just cant figure out where I’m going wrong. Any help is appreciated!

P.S. I wanted to upload the file but it’s too big so i’m not sure how