It seems starange issue as we can not re-produce in house. FontSet() Token API should not interfere with print behaviour.
May be you can try to re-produce the bahaviour manually without the Applet by creating a message, change the font and size then type the “Hello World” and finally print. May be you can try to re-produce it in another machine with different printer.
Let us know if you have any positive suggestions from the GroupWise community.