Sender for ttl exiting prematurely

[boilersam]

On a CentOS 7 VM with a single CPU, I get messages about the TTLs exiting prematurely.
Any idea what causes this or a work around?

$ sudo ./fbtracert -v 3 -showAll -logtostderr=true -maxTTL 10 -maxSrcPorts 32 10.0.2.3
Using as source address: 10.0.2.15
Starting fbtracert with 96 probes per second/ttl, base src port 32768 and with the port span of 32
I0111 18:00:25.276544 28249 main.go:321] Sender for ttl 1 starting
I0111 18:00:25.285238 28249 main.go:321] Sender for ttl 2 starting
I0111 18:00:25.291811 28249 main.go:321] Sender for ttl 3 starting
I0111 18:00:25.310730 28249 main.go:321] Sender for ttl 4 starting
I0111 18:00:25.314622 28249 main.go:321] Sender for ttl 5 starting
I0111 18:00:25.316734 28249 main.go:321] Sender for ttl 6 starting
I0111 18:00:25.320090 28249 main.go:321] Sender for ttl 7 starting
I0111 18:00:25.322321 28249 main.go:321] Sender for ttl 8 starting
I0111 18:00:25.327058 28249 main.go:321] Sender for ttl 9 starting
I0111 18:00:25.329369 28249 main.go:321] Sender for ttl 10 starting
I0111 18:00:25.331775 28249 main.go:234] ICMPReceiver is starting...
I0111 18:00:25.345787 28249 main.go:116] TCPReceiver starting...
I0111 18:00:25.961111 28249 main.go:386] Sender for ttl 6 exiting prematurely
I0111 18:00:25.961315 28249 main.go:386] Sender for ttl 10 exiting prematurely
I0111 18:00:25.961745 28249 main.go:386] Sender for ttl 9 exiting prematurely
I0111 18:00:25.961836 28249 main.go:386] Sender for ttl 8 exiting prematurely
I0111 18:00:25.998987 28249 main.go:386] Sender for ttl 7 exiting prematurely
I0111 18:00:28.408230 28249 main.go:386] Sender for ttl 5 exiting prematurely
I0111 18:00:29.483850 28249 main.go:386] Sender for ttl 4 exiting prematurely
I0111 18:01:27.899125 28249 main.go:390] Sender done
I0111 18:01:27.900043 28249 main.go:390] Sender done
I0111 18:01:27.930817 28249 main.go:390] Sender done
I0111 18:01:27.930897 28249 main.go:618] All senders finished!
I0111 18:01:29.931271 28249 main.go:278] ICMPReceiver done
I0111 18:01:29.931335 28249 main.go:199] TCPReceiver terminating...