CPU: Ryzen 1700
GPU: R7 260X 2GB (driver 18.5.1)
OS: Win10 Pro

Confirmed this occurs on both Cemu 1.12.0d and 1.13.1.
I'm currently playing on 1.12.0d because it has less stutter triggers. This is with the latest cemuhook and shader cache.

Basically whenever I cut grass or it gets destroyed in any way, it will cause the game to stutter badly. I'm talking 1-5sec freezes, usually two in a row. It gets particularly bad when fighting Lynel due to their fire breath burning lots of grass. It doesn't happen every time but it's very frequent.

Unrelated to grass... but I've also noticed stuttering when animals get spooked and start running into things. At one point, I had a fox run up a steep hill during which I've also experienced stuttering. I'm not sure if it's related but I think it could be a collision issue.