IAX trunks - one way calling only?

Changed a server (and copied and pasted trunk settings from one PIAF to another)and now trunking only seems to be one directional to and from that particular endpoint. I created another ‘test’ trunk LC-2 to ‘play’ with.

Show Peers:

From Server ROS
MID/7006 4569 OK (82ms)
LC-2/7002 4569 OK (54ms)
LC/7008 4569 OK (53ms)
DUR/7007 4569 OK (117ms)

from Server LC
MID/7006 4569 OK (66ms)
ROS-2/7002 4569 OK (56ms)
ROS/7008 4569 OK (55ms)
DUR/7007 4569 OK (123ms)

Calls from LC server work perfectly (outgoing). Incoming from other locations - never hit the LC server. Always get a s-CHANUNAVAIL error on other server.
However, call between any other servers work perfectly. ROS can call MID and DUR just fine (and vice-versa)

ROS Server - asterisk 1-4.21.2 zaptel
LC server - asterisk 1-4.26.3 zaptel

Any good methods on dissecting this problem?