Thank you for your post.
When creating labels in FileMaker Pro, the layout is expecting the labels to be a specific height and consistent distance between each label. If the labels "are not evenly spaced across and down the pages", then you would definitely have a problem. One option is to create separate layouts to print to one set of labels, and another layout to print another set of labels, each relating to different distances on the labels. If you cannot find anything consistent with label distances, then you may have to have a separate layout for each label.
I could be wrong, but I think the OP was saying that the filemaker output was not evenly spaced rather than the labels themselves.
We've seen "label creep" happen before. Usually using the object info palette to "tweak" the size of the layout parts one pixel at a time will solve the issue for vertical spacing issues, though what would cause uneven horizontal spacing is a mystery to me.
That is correct. The labels themselves are consistently spaced, but I cannot get the output to print on the labels correctly, even with small pixel changes.
This is the type of problem that can often be easily solved if the layout itself could be examined, it's part dimensions compared to the physical dimenions of the label sheet and the data being printed on the labels checked for issues.
Trying to spot specific problem via this forum, on the other hand, can be extremely difficult.