SIP Phone - Delay before AGI execution

Hi guys,

I have 5 SIP endpoints connected to Asterisk. 2 IP Phones, 1 Sipdroid and 2 softphones for PC.
My dialplan uses the Asterisk AGI just after one special number is dialed and my application says 2 numbers.

On all my device except 1 IP Phone, I can hear these 2 numbers imediatly after I dial the number. The problem is that this IP Phone is the one we want to use. We have to wait 5s for hearing these numbers.

This phone is the linksys spa 901, maybe someone has an idea about the origin of this problem. Thank you very much.

Best Regards,

Vincent Roye.