Hi, Sadie,
This is hard to say for certain but I suspect it is more of an issue with the spec you're using to print the Additional Form with.
Suggestion: We provide a few different Additional Forms specs with AP sample data. If you don't already have one of these forms available within your dataset, why not open the spec designer and select File | Open Template and then one of Additional Form or Payment Advice - 35 lines. Save the spec into your dataset using your data extension.
Then, try printing or emailing or previewing an EFT Additional form again using the new spec and see what happens. Everything should work out okay. It does here when I use any of those specs.
After, you can compare the new spec with the one you're using.
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Regards,
Softrak Tech Support