Blob Shadow quality degrades each time it's rendered on a new mesh on mobile.

I’ve created a blob shadow using a material and material function, it works perfectly on PC and for a moment on mobile, but when my character moves over a new mesh the quality degrades slightly and gets slightly more pixelated, when my character has moved over about 20 meshes it just disappears. I don’t know much about rendering and shadows but I guess it’s a problem with GPU memory and the shadow rendering on everything it touches and so every time it touches a new mesh it takes up more rendering power. So I hope the fix is just a checkbox somewhere that changes how it renders.