SIP call clearing & PAP2-NA

I’m not entirely sure if this is an Asterisk problem, or a Linksys issue. Either way, I’m hoping someone has run into this before.

I have a few PAP2-NA devices connected to an Asterisk box via both LAN and the Internet. All is running perfectly. However, I’m having an issue where my PAP2-NA’s are not clearing their channel and hanging up when the far-end hangs up first.

Doing a debug on SIP I see Asterisk send “BYE” to the PAP2-NA, and I see a “BYE” response coming back, but the PAP2-NA doesn’t seem to do anything after. The line remains dead for a short time and then eventually I get a fast-busy as if the phone was left off the hook.

Anyone have any thoughts?