This problem drove me to the edge of insanity, and I couldn't understand what I was doing wrong. Everytime I was playing "Animal Drivers" and turning a corner where new models and textures needed to be loaded to the GPU, there was a very clear 0.5s-1s delay in the editor / on the device (less clear here though).
So if your game has this issue, here's all you have to do:
1. Create a script or just add it to one of your existing ones.
2. Put Shader.WarmupAllShaders(); in your Start function.
That's it! Fixed!
Make sure this runs at the start of your level, and all will be well.