Unwanted patches of colour in Matlab EPS and PDF figures

I have a figure produced using the image function in Matlab 2014b. The image looks perfect in the figure window, but when I save it to a PDF or EPS file, it produces patches of colour that don't appear in the figure window. When using export_fig, this happens in both the PDF and EPS file formats, and when using print, it only shows up in the EPS file, not the PDF. However, some other weird stuff happens using the print function, so I would prefer not to use that.

The figure is a 3 x 4 set of maps, and the extra patches of colour can be seen in the snapshot below (at the bottom of each map and to the right of the MJJ map). I have been deleting them by hand in Illustrator, but I have a large amount of these figures so I need to stop it happening at the Matlab end really.

Does anyone know what is going on with this and how to fix it?

FYI, this is the code I am using to make the figures (amongst other lines to get it to look exactly like this):

h=image(lon_data,lat_data,plot_data);

And this to export the figures:

export_fig(filename,'-painters','-eps','-pdf','-r600')

Edited to add: this is how it should look - no extra bits at the bottom or sides of the maps. Sometimes the bit to the right happens further down too.