=== Repro ===

i. Download attached el file
ii. Read it to ensure I am not hacking your computer
iii. In the same directory run

emacs -Q --eval '(progn (load-file "line-repro.el") (message (format "%S"
(repro))))' -nw --batch

As the last line of output I get

(3005 4100 6006)

I wouild expect this 4100 to be 5005

The third value indicates it is the line that gets truncated rather than
the string

=== Version details ===

In GNU Emacs 24.5.1 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9) of
2016-04-08 on binet, modified by Debian Windowing system distributor `The
X.Org Foundation', version 11.0.11804000 System Description: Debian
GNU/Linux testing (stretch) Configured using: `configure --build
x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
--libexecdir=/usr/lib --localstatedir=/var/lib --infodir=/usr/share/info
--mandir=/usr/share/man --with-pop=yes
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
--build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
--libexecdir=/usr/lib --localstatedir=/var/lib --infodir=/usr/share/info
--mandir=/usr/share/man --with-pop=yes
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
--with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g
-O2 -fstack-protector-strong -Wformat -Werror=format-security -Wall'
'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro' Important
settings: value of $LANG: en_GB.UTF-8 locale-coding-system: utf-8-unix