Displayed plot is scaled by 0.5 in X axis?

I am having a strange problem with loading gcode on my mill. The X axis shows the gcode scaled down by a factor of 2. I have checked the gcode itself and it is fine. In the example image, the X and Y axis extents should be about the same but the X axis ends up being half of the Y axis.

I am running LinuxCNC 2.7.8 and I can't see anything obvious in the configuration that would do this. The problem also persists if I switch the GUI to Axis, so I don't think this is an interface problem.

Does anyone have suggestions to resolve this?

It turns out that this was a PEBKAC problem. I used a config from my lathe as a basis when upgrading my mill to use the Mesa cards and had a G7 in my RS274NGC_STARTUP_CODE. This caused the X axis to be scaled by 50% as it thought it was in diameter mode. I would not have expected a G7 to be valid in mill mode, but I guess that to the interpreter there is no real difference. All is working normally now