This has to be the weirded bug.
I've got a 4801 that was running 1.3b9 - when I run mtr with a count
greater than 32 it starts showing 100% packet loss at the 4th hop from
the 32nd pass onwards. 0-31 are fine then bang it fails. Always the
4th hop, always the 32nd pass. Even if I pick a different target which
has a different 4th hop it still fails at the 4th hop.
I uploaded mtr to the firewall and ran it there and it worked fine. It
only show up from clients on the lan side.
I downgraded to 1.233 and the problem went away.
Disabling traffic shaping didn't change anything.
To reproduce run "mtr --report -c 64 www.google.com" from a host on the
lan side of a 1.3b9 firewall.