My Makerbot Mini has been leaving parts of the print out. I've attached a couple of examples of this occurring:

IMG_0011.jpg IMG_0012.jpg
The first image is the one with the problem while the second is what it should be looking like.
IMG_0013.jpgIMG_0014.jpg


While watching it print, I noticed that upon reaching a section that it misses out, the extruder moves upwards about 0.5cm and it stops extruding any plastic. It then moves along horizontally until it reaches the end of the missing section and then moves back down and carries on as if nothing happened. As can be seen in the images, it happens multiple times in the same X-Y position with different layers. This has happened a couple of times now with completely different models (it has happened on both straight lines and curved lines too).
After looking through some 3D printing troubleshoot guides, I haven't seen anything similar to this. Has anyone had a problem like this or maybe even know of a way to fix it?
I was thinking it might be a software problem with the way the extruder purposefully avoids the area. If it makes any difference, I use 123D Design to create the objects and export them as an .stl file and then print using makerbot desktop.