Xerox DocuPrint N3225 System Administrator Manual page 126

Using Custom Paper Sizes
1-118 System Administrator Guide
If the leading edge width of the non-standard size being used
differs from that of the standard size selected in the Custom
Setting by more than 1/4 inch, it will not be possible to use the
Duplex or Stapler options.
To prevent the printer from incorrectly loading standard paper
from one of the regular input trays when the Custom Size
setting is the same value as the auto-detected size in that other
input source, you must exclude the Multi Bypass Feeder from
the Tray Sequence setting and specifically select that the Multi
Bypass Feeder as the input source.
Refer to Table 1.34 for usage examples.