Window size in TruClient playback under load is decreasing

Window size in TruClient playback under load is decreasing

LoadRunner 12.01, windows 7.

We have the "Non-interactive window size" set to 1280x1024 (screenshot attached) in VuGen, and the equivalent setting in the run-time settings in the controller but as per the screenshots we get when an error happens the width of the window has shrunk which means that the mobile/tablet version of the site is being displayed which means that the buttons we scripted for are no longer there.

How can we get this to work?