SLA help: Zap trunk, Zap & SIP stations

I’m having trouble getting SLA to work. My set-up is as follows:
TDM400 card: fxs_1, fxo_4

I’m looking to have the Zap/4 act as the shared trunk line for a SIP device and my analog phones on Zap/1. When I call in, I see the following:

-- Executing [s@line1:1] SLATrunk("Zap/4-1", "line1") in new stack -- Created MeetMe conference 1023 for conference 'SLA_line1' -- Called spa942_s -- Called 1 -- SIP/spa942_s-081d3648 is ringing -- Zap/1-1 is ringing -- Zap/1-1 is ringing -- Zap/1-1 is ringing -- SIP/spa942_s-081d3648 answered -- Hungup 'Zap/1-1'

The call comes in, I answer it on my Linksys SPA942 and Asterisk seems to automatically hangup on Zap/1. When I pick-up an analog phone, I get dial-tone… I’m not joined to the conversation.

Here are my config files:
sla.conf

[code][line1]
type=trunk
device=Zap/4

[station1]
type=station
device=SIP/spa942_s
trunk=line1

[station2]
type=station
device=Zap/1
trunk=line1[/code]

zapata.conf

[code][channels]
usecallerid=yes
callerid=asreceived
callwaiting=yes
echocancel=yes
echotraining=yes
immediate=no
busydetect=yes
busycount=5

context=sla_stations
signalling=fxo_ks ; use FXO signalling for an FXS channel
mailbox=501@default
channel => 1

context=line1
signalling=fxs_ks
channel => 4[/code]

sip.conf

[spa942_s] type=friend regexten=102 mailbox=501@default checkmwi=60 username=spa942_s secret=**** context=sla_stations host=dynamic nat=no port=5063 canreinvite=no qualify=yes disallow=all allow=ulaw allow=gsm dtmfmode=rfc2833

extensions.conf

[code][line1]
exten => s,1,SLATrunk(line1)

[sla_stations]
exten => station1,1,SLAStation(station1)
exten => station1_line1,1,SLAStation(station1_line1)
exten => station1_line1,hint,SLA:station1_line1

exten => station2,1,SLAStation(station2)
exten => station2_line1,1,SLAStation(station2_line1)
exten => station2_line1,hint,SLA:station2_line1[/code]

Any help would be greatly appreciated!