MakerBot 2X - offset rafts

Hello,

I'm posting on behalf of a maker space in Canada. We received 2 identical MakerBot 2X units and have spent the past little while working out the bugs.

I went to print some stuff the other day when I noticed that the body of the print was offset from the automatically generated raft. The raft printed normally but then when it moved onto the body layer, it printed forward (to the front of the bed) around 1/2" (based on the position of the edges of the raft and print and the locations of circular holes in the print). Weird thing: it only happened on 7/8 objects. I checked the print preview in the software and it seemed to be fine.

This was using default settings for raft. *This has only been happening on one of the two printers*. We tested using 2 different sets of parts from the same source online. Talked to Kerry Stevenson (founding writer of Fabbaloo) and he was as puzzled as we were. We also have a small team of people who are moderately knowledgeable about 3D printers, no ideas from them yet either.

Thoughts?
-John