Can't blend 3 material functions in a material?

Hi, I’m trying to vertex paint a wall model with 3 material functions. I’m using material blend standard node to blend these materials. However, when I blend the third material function with the result from the first two functions, the output of the material goes to default checkerboard pattern after shader compiling is complete. Is this an engine limitation or a bug? If it is a limitation, is there a way I can get around this? PS, I can use material blend simple node to blend 3 func s successfully but that doesn’t blend the normalmaps.