On Solaris 10 e1000g interfaces (and possible others) it might happen that an unexpected FCS (Frame Check Sequence) is being received from the interface file descriptor. This is in turn causes packet drops on the outgoing side since the Ethernet MTU of 1514 bytes gets exceeded by those 4 Bytes for large packets.
Setting the parameter outmtu to 1514 as follows is a suitable workaround in this situation:
# bng control 10 BalanceNG: connected to instance 10 PID 6425 bng# set outmtu 1514 bng# save