Busy lines with some FXO ports - Digium TDM400

I have an odd behaviour with my asterisk server. I have 5 analogue lines, and 2 Digium Cards ( one card with 1 FXO and 1FXS, and the other with 4 FXOs). The thing is that there is one FXO port that only works with one specific line. If you try with another line it gets busy.
I have Asterisk at Home 2.7, but I have upgraded Asterisk to version 1.2.10 and Zaptel 1.2.8


Here is my /etc/zaptel.conf

Autogenerated by /usr/local/sbin/genzaptelconf – do not hand edit

Zaptel Configuration File

This file is parsed by the Zaptel Configurator, ztcfg

It must be in the module loading order

Span 1: WCTDM/0 “Wildcard TDM400P REV I Board 1”

fxoks=1

channel 2, WCTDM, inactive.

channel 3, WCTDM, inactive.

fxsks=4

Span 2: WCTDM/1 “Wildcard TDM400P REV I Board 2”

fxsks=5
fxsks=6
fxsks=7
fxsks=8

Span 3: ZTDUMMY/1 “ZTDUMMY/1 1”

Global data

loadzone = us
defaultzone = us


And my /etc/asterusk/zapata.conf
;
; Zapata telephony interface
;
; Configuration file

[trunkgroups]

[channels]

language= es
context=from-pstn
signalling=fxs_ks
rxwink=300 ; Atlas seems to use long (250ms) winks
;
; Whether or not to do distinctive ring detection on FXO lines
;
;usedistinctiveringdetection=yes

usecallerid=yes
hidecallerid=no
callwaiting=yes
usecallingpres=yes
callwaitingcallerid=yes
threewaycalling=yes
transfer=yes
cancallforward=yes
callreturn=yes
echocancel=yes
echocancelwhenbridged=yes
echotraining=800
rxgain=8.0
txgain=0.0
group=0
callgroup=1
pickupgroup=1
immediate=no

;faxdetect=both
faxdetect=incoming
;faxdetect=outgoing
;faxdetect=no

;Include genzaptelconf configs
#include zapata-auto.conf

;Include AMP configs
#include zapata_additional.conf


and /etc/asterisk/zapata-auto.conf

; Autogenerated by /usr/local/sbin/genzaptelconf – do not hand edit
; Zaptel Channels Configurations (zapata.conf)
;
; This is not intended to be a complete zapata.conf. Rather, it is intended
; to be #include-d by /etc/zapata.conf that will include the global settings
;
callerid=asreceived

; Span 1: WCTDM/0 "Wildcard TDM400P REV I Board 1"
signalling=fxo_ks
; Note: this is an extension. Create a ZAP extension in AMP for Channel 1
context=from-internal
group=1
channel => 1

; channel 2, WCTDM, inactive.
; channel 3, WCTDM, inactive.
signalling=fxs_ks
; Note: this is a trunk. Create a ZAP trunk in AMP for Channel 4
context=from-pstn
group=0
channel => 4

; Span 2: WCTDM/1 "Wildcard TDM400P REV I Board 2"
signalling=fxs_ks
; Note: this is a trunk. Create a ZAP trunk in AMP for Channel 5
context=from-pstn
group=0
channel => 5

signalling=fxs_ks
; Note: this is a trunk. Create a ZAP trunk in AMP for Channel 6
context=from-pstn
group=0
channel => 6

signalling=fxs_ks
; Note: this is a trunk. Create a ZAP trunk in AMP for Channel 7
context=from-pstn
group=0
channel => 7

signalling=fxs_ks
; Note: this is a trunk. Create a ZAP trunk in AMP for Channel 8
context=from-pstn
group=0
channel => 8


This problem is with port number 4