yes, i triple checked to make sure that both the remote router and our firewall have those ports open.
i did end up finding the solution today though. it was in the same vein as RTP transmissions, but it was Peer RTP. i had to use sip debug to find what port the Peer RTP was transmitting for the calls, and it changes every time a call is placed, so i just opened a wide range on the remote machine and the problem was fixed.
the range i opened was 2200 - 2299 TCP/UDP. It didn’t specify, but I’m assuming that it’s UDP just like the other RTP transmission.
Anyways, if anyone else has the same issue, that’s how to fix it
How to really fix it is to have /etc/asterisk/rtp.conf match the ports that you open on the router, you need two ports per concurrent call so 10000-20000 is usually much too big.