Our support team says:
"This is most likely occurring because the offset is not defined properly for each of the Cam documents. The user should go to File > CAM, select the first Photoplot file, click Edit, click Options. Make sure the Justification is set to Offset and enter x and y offset values that roughly center the board in the plot area. Make sure the scaling is set as 1 to 1. Edit all the rest of the Photoplot documents making sure that the same x and Y offset values are defined for each CAM document. The NC drill file should also be set with the same x and y offset values. Doing this will make all the Gerbers line up with each other when loading into a Gerber Editor."
You can also log a support request for this type of question.