This problem has to do with the order of evaluation of the error regular expressions. If you don't add your error regex, SlickEdit finds the wrong file. Also, if you add your error regex at the bottom (last), SlickEdit as expected still finds the wrong file. However, if you move your error regex to the top of the list, then SlickEdit finds the correct file.
I put your error regex in the "User" folder and then moved that folder to the top. Once I did that, SlickEdit finds the correct file.