Did you first use Printer Setup to specify a different page size than that specified for printing a label?
I solved this issue years ago, maybe FMP 10 - but on a Mac, by scripting all printing. In every script was a page setup and again in the print dialogue.
In the two set up dialogues I set the page size (label for the dymo) etc., then again in the print choices.
I tested the scripts by first not checking the box, "perform without dialogue" just to check. Worked like a charm.
Now, I'm in FMP12, in Windows 7, and the scripts can't remember these setting, and always revert to the last setting.
I posted this on this forum a week (couple of weeks?) or so ago and found that without 3rd party software, FMP will no longer do this, at least on Windows, but you might try the scripting on a Mac.
As Phil suggests, I think you just have to manually print, when changing printers, and re-check the settings.
Page setups and prints in the scripts do still work fine on a Mac with FMP 13 so that's the solution. The ultimate would of course be to not have to go through page setup each time, especially when we're busy, but maybe later!
Thanks for your suggestions - greately appreciated.