colorSurf depthSurf width and height error in the Editor

I have a data visualization piece of code that instantiates a bunch of prefabs and then shows/hides meshes and re-colors pieces according to values. For some reason, I see the following error scrolling on my screen in the editor while running:

 colorSurf->width == depthSurf->width && colorSurf->height == depthSurf->height
 (Filename: C:/BuildAgent/work/b0bcff80449a48aa/Runtime/GfxDevice/threaded/GfxDeviceClient.cpp Line: 1611)

How can I find out what is causing this? I could only find reference to some sort of shader issue but I am not using any particularly interesting shaders that I know of.

More strange behavior - I added a copy of the prefab to the scene and it was fine, I tried running with it in the scene and it was still fine. Then, I don't know what happened but when I tried that again I found I would get the same error if I selected a particle emitter within the prefab. I added a blank particle emitter, and the same error kept scrolling. To sanity check, I closed the project, opened a different project, tried adding a basic particle system and all was well. So, I go back to main project, error gone for particle emitters, but still there at runtime.

I have changed nothing since 3.4 and all was well then - is this an editor only bug, is this something I need to action? How can I tell what's causing it?

The only thing I am doing to set the color on the object is take a variable that I set in the inspector with the selected color:

 public Color selectedColor;

then apply that to the object as follows:

 serverModel.renderer.material.color = selectedColor;

I'm using basic standard diffuse shaders on the server model, if that makes any difference. Finding it hard to pinpoint this one, so any help or ideas would be appreciated!