Call Forwarding Issue

[Iceey]

I have setup an inbound route that route incoming call to custom destination which is another SIP URI.

Below is my config:
[custom-dial-sip-uri]
exten => s,1,NoOp(Dialing External SIP URI)
exten => s,n,Dial(PJSIP/signalwire_sip,r)
exten => s,n,Hangup()

[signalwire_sip]
type = endpoint
context = from-internal
disallow = all
allow = ulaw
aors = signalwire_sip_aor

[signalwire_sip_aor]
type = aor
contact = sip:7axbb4xbxa12x11x--0@daily-7x4bbx4xbb12cx12-pinless-sip.dapp.signalwire.com

This configuration is fine but the issue is sometimes like 10% of the call have issue.
The call is successfully route but each end of the call cannot hear the sound from the other end.
What may the issue?

[Iceey]

Actually I am running FreePBX on AWS instance. And yes I set my public IP at External Address at NAT Settings.

The RTP Port Ranges is 10000 - 20000 and my instance allow UDP port 10000-2000 and 5060-5061 to be access by public.