🚀 go-pugleaf

I am getting a strange result when I try to change the footer margine
in nroff using the ms package.  Here is an example

.ND
.nr HM 3v
.nr FM 1v
.nr LL 70n
.LP
0101010101010101010101010101010101010101010101010101010101010101010101
0202020202020202020202020202020202020202020202020202020202020202020202
   .
   .
 about say 70 line like this with no blank line in between
   .
7070707070707070707070707070707070707070707070707070707070707070707070

The result is that at the end of the page I have

5858585858585858585858585858585858585858585858585858585858585858585858
5959595959595959595959595959595959595959595959595959595959595959595959
6060606060606060606060606060606060606060606060606060606060606060606060

6161616161616161616161616161616161616161616161616161616161616161616161


  	  		        -2-
6262626262626262626262626262626262626262626262626262626262626262626262
.
.


Clearly the line 61 should come before the 1st blank line.  If I set
the FM to 2v then the error does not occur.  But if set to 0 then the
blank line occurs at 59 followed by line 60 and 61 followed by new
page.


I have tried this on Pyramid (BSD 4.2 and SYS V), Convex (BSD 4.2) and
SUN 3.  All with the same result.  Can someone enlighten me?