🚀 go-pugleaf

I'm getting fairly frustrated with some erratic behavior with SCRIPT-VS's
column-balancing feature.  What's happening is on the last page of a
section (where column balancing might come into play) and the second
column of a two-column page is non-empty, the line-spacing of the first
column is compressed if column-balancing is turned off (.bc off).  The
number of lines in the column looks about right, but they are too close-
ly-spaced.  The second column is normal.  Removing the .bc off control
word makes everything ok, except that I don't want balanced columns.
I'm reproducing without alteration the first part of the SCRIPT file
below.  The problem first shows up in formatting the imbedded text
CRKDN-P SCRIPT (which contains no control words except :p., .bf b, and
.pf).  The offending ".bc off" is right after the line with the URL.
Putting it after the .cl line makes no difference.

SCRIPT (V 4.0.0) is being called with a DEV(PSA) option.

I'm not expecting that anyone will debug my code for me, but I was
hoping that someone might have run into this before and be able to shed
some light on the matter.  SEARCH SCRIPT-L FOR .BC OR "BALANCE COLUMNS"
turned up nothing at all.
-----------------------------------------------------------------------
.se bodyfont = 'Times Roman'
.se SYSVARX = 'no'
.df n type(&bodyfont. 11)
.df b type(&bodyfont. bold 11)
.df i type(&bodyfont. italic 11)
.df bi type(&bodyfont. bold italic 11)
.im splchars;.im symbols;.im dingbats
.if SYSOUT = PS
.th .go ps
.pm 1.0i;.ll 6.0i
.se emdash = '--';.se endash = '-';.se d5A = '*'
.go common
... ps
.pm 1.25i 0.75i;.ll 6.5i;.bf n
.ti [ B0;.ti ] 6A;.* Interpret brackets correctly.
... common
.fo on;.pn on
:frontm.
:titlep.
:title.The Hacker Crackdown;.br;Law and Disorder on the Electronic Frontier
:date.January 1, 1994
:author.Bruce Sterling
:address.
:aline.bruces@well.sf.ca.us
:eaddress.
:etitlep.
.sp 2.5i
.ce Copyright &cpyrtserif. 1992
.ce Bruce Sterling
.ce Austin, Texas
.sp
.ce Literary Freeware:  Not for Commercial Use
.ce URL:  http://ice-www.nasa.gov/ICE/papers/hacker-crackdown.html
.bc off
.cl 3.0i;.cd 2 0.0i 3.5i
:preface.
.im crkdn-p
.cl 6.5i;.cd 1 0.0i
:toc.
:body.
.cl 3.0i;.cd 2 0.0i 3.5i
:h3.CHRONOLOGY OF THE HACKER CRACKDOWN
<etc., etc., etc.>
-----------------------------------------------------------------------
By the way, the book itself (The Hacker Crackdown) makes very interesting
reading indeed.  The URL above will get you to it.
                                             /b