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One fax that was received, might have had a legal-size or 11 x 17 inch page included in it / scanned in as a part of the fax.
That would require 11 x 17 paper to print out.
Mixing legal size into regular size, in a fax, is often necessary for inclusion of legal forms, but causes trouble as you can tell.
Try loading more than one 11 x 17 sheet at a time, see if there's more than one to print, then have it resume printing 8 1/2 x 11 sheets.
At worst, faxes might have to be cleared from the K-M machine's memory, for this problem to be cleared up altogether.