This is a problem with UDP under Windows, it considers a packet "sent"
when the sendto() call is made, not when the packet has actually hit
the wire. So if sendto() is called too rapidly (e.g. when collector
update packets are split) you can lose the previous UDP packet if it
hasn't really been sent yet.
What we did was add "D_NETWORK" to the MASTER_DEBUG and STARTD_DEBUG
flags in the config file. The added delay of logging the UDP packets
seems to be enough to keep this from happening.
You can alternatively use "UPDATE_COLLECTOR_WITH_TCP = True" and avoid
UDP entirely.