Can you get the output of "show chassis hardware" command? Are there any chassis alarms currently active in "show chassis alarms"? Do you see errors in syslog messages?
Also, can you confirm if this the topology -
Ixia-1 <----> et-5/1/2 ---- et-5/1/5 <----> Ixia-2
How did you learn of the packet loss (apart from the show interfaces extensive command output)? Can you configure a traffic flow on Ixia-1 to send 1000 packets to Ixia-2 and see how many you recieve?
If there are drops on ingress-side on et-5/1/2, we might be able to trace them, depending upon the hardware config.