tcptraceroute libnet_write failed? Attempted to write 40 bytes, only wrote -1

Hi!

I tend to use tcptraceroute a lot when troubleshooting link connectivity, with me being a newb and all.

I noticed whenever I try to tcptraceroute to a greater than 1024 port, or a port number with more than 3 characters (eg 8443 instead of 443, or 9443 instead of 80),

or also from an interface with a public address, to an IP with a private address, or a combination of the above the UTM9  tcptraceroute returns 

for example:

tcptraceroute -s 65.X.X.X -i eth1 10.20.X.X 8443

Selected device eth1, address 65.X.X.X, port 41559 for outgoing packets
Tracing the path to 10.20.X.X on TCP port 8443 (pcsync-https), 30 hops max
libnet_write failed? Attempted to write 40 bytes, only wrote -1

tcptraceroute -s 10.25.X.X -i eth2 10.20.X.X 8443
Selected device eth2, address 10.25.X.X, port 56858 for outgoing packets
Tracing the path to 10.20.X.X on TCP port 8443 (pcsync-https), 30 hops max
libnet_write failed? Attempted to write 40 bytes, only wrote -1

tcptraceroute -s 10.25.X.X -i eth2 10.20.X.X 844
Selected device eth2, address 10.25.X.X, port 35328 for outgoing packets
Tracing the path to 10.20.X.X on TCP port 844, 30 hops max
libnet_write failed? Attempted to write 40 bytes, only wrote -1

These work:

tcptraceroute -s 65.X.X.X -i eth1 10.X.X.X 443
Selected device eth1, address 65.X.X.X, port 57464 for outgoing packets
Tracing the path to 10.X.X.X on TCP port 443 (https), 30 hops max
1 * * *
2 * * *
3 * * *
4 * * *

tcptraceroute -s 10.25.X.X -i eth2 10.20.X.X 80
Selected device eth2, address 10.25.X.X, port 45223 for outgoing packets
Tracing the path to 10.20.X.X on TCP port 80 (http), 30 hops max
1 10.25.X.X 1.455 ms 1.297 ms 1.166 ms
2 *^C

Why does this happen and what can I do to avoid it?