I found the secret for getting Yam to print a message. The following is I hope a useful tip.
Leave print text as graphics without change. Instead go into .config of Yam with an editor and alter the line
for print check from Y to N. that seems to do the trick. Do not forget to save your .config..
I have this printing issue when using a printer which requires "print text as graphics" option (from Printer prefs). Using a printer with a real text mode I don't have this issue.