Linear Analysis of Simple Simscape circuit

Hi, I'm trying to use the Linear Analysis tool to provide me with the frequency response of analogue circuitry drawn in Simscape. The original circuit is more complex, but I've reduced the problem to that of a simple Resistive divider and capacitor.

With the capacitor removed, and the resistors equal, the Bode plot from the Linear Analysis tool gives the correct answer (-6dB). However when the capacitor is added the Bode plot has the wrong gain. (the pole freqeuncy is also wrong).

If I run the sinusoidal input at chosen discrete frequencies the attenuation as measured by comparing the scope waveforms is correct.

What is the error in my use of the use of the Linear Analysis Tool?

Thanks,

David.