The specular of glass on the mirror is incorrect.The superposition algorithm is wrong.
(The label has been unchecked opaque)
We found the answer.
Maybe that's the reason
Arnold calculates the object first and then HDR, which results in the superposition problem
HDR is not involved the IOR in the specular, so it is impossible to get the correct image. It is necessary to turn off the specular in HDR
Or Transparency Depth ≤ 1
And Emission can get the correct IOR in the specular