lpr loses last part of output

[Jerry N Sweet]

We have a Printronix P6040L printer hooked up to the ALM-2 parallel port
on a Sun 3/260 running SunOS 4.0.1.  About half the times that lpr is used
with plain text, the very last part of the output is mysteriously
truncated.  The problem is reproducible with certain files.  Has anyone
else run into this one---and fixed it?  There doesn't seem to be anything
special in /etc/printcap that needs to be set, but perhaps I'm missing
something.  Here's the entry:

0|lp|printronix|Printronix P6040L:lp=/dev/mcpp0:sd=/var/spool/lpd:\
	:pl#66:pw#80:fo:df=/i/dvi/dviprx:

I'm not 100% certain it's not a problem with the printer itself; to make
the P6040L work with the ALM-2 parallel port, certain resistors in the
printer's Centronics interface had to be exchanged for others in a
standard, documented way.  But I'm not a hardware person; I know not to
stick my fingers in light sockets and how to pull socketed chips, and
that's about it.

The only work-around we can think of is to append a big "END OF FILE"
banner to the output.  This seems to work fairly reliably, but it's icky.