On High End devices (SRX3000 and SRX5000), when running traceroute, some of the hops will time out, as a result of TTL Expire.
On Junos 10.3, when running SRX high end (SRX-3400, SRX-3600, SRX-5600, SRX-5800), it has been observed that some of the hops in a traceroute will time out. It was found to be as a result of incorrect processing of embedded ICMP packets when using multiple SPC's, and with NAT translation involved. The embedded ICMP packet was being sent to the wrong SPC, and this has been fixed in Junos 10.4R2 and above. If using a single SPC, or on branch platforms, you will not see the same problem.