Argument buffer participates in modification as well as resource use

Has anyone seen this error when debugging a vertex shader in Xcode for Metal?

I'm using an Argument Buffer that looks like this:

struct VertexTriArgBufferB {

constant Uniforms *uniforms [[ id(WKSUniformArgBuffer) ]];

constant UniformDrawStateA *uniDrawState [[ id(WKSUniformDrawStateArgBuffer) ]];

constant Lighting *lighting [[ id(WKSLightingArgBuffer) ]];

constant RegularTextures *tex [[ id(WKSTextureArgBuffer) ]];

};

Passed in to the vertex shader like so:

vertex ProjVertexTriB vertexTri_multiTex(

VertexTriB vert [[stage_in]],

constant VertexTriArgBufferB & vertArgs [[buffer(WKSVertexArgBuffer)]])

{

.....

}

The full error message is:

Error DYPShaderDebuggerErrorDomain:2:

Error creating instrumented render pipeline state: Error Domain=AGXMetalA12 Code=3 "buffer(0): Argument buffer participates in modification as well as resource use" UserInfo={NSLocalizedDescription=buffer(0): Argument buffer participates in modification as well as resource use}