While working on a level, I went to edit the specular constant in my landscape material, and when I applied it, while building shaders, there was an error message that I didn’t notice until the last second at the bottom right but it said something along the lines of “framerate has been below 10 for X time”. After that any animations (trees, particles,etc.) started to lag, and completely stop when my camera is still. In-game is perfectly fine, only in the editor.