One of the BR Mk1 compartment break seems to have a mixed up (or turned around) image.
See the trains pulled by 5MT on the westward track in the screenshot linked below:http://forum.simutrans.com/index.php?topic=6375.msg85939;topicseen#msg85939 (http://forum.simutrans.com/index.php?topic=6375.msg85939;topicseen#msg85939)
compiled from your git repository yesterday
Are you referring to the one with the darker roof?
yes indeed.