Pfflowd: missing traffic

[kart0ffelsack]

I have 4 Wan and 1 Lan port. The wan ports are all in a load balancer pool.

I tried to use pfflowd together with nfdump to monitor the traffic of hosts from the lan site to the wan site. But for some reason not all traffic is reported. For example if a host downloads 4 200MB files sometimes nfdump only shows a total of 400MB traffic and sometimes it shows all traffic and sometimes none…

I suspect that pfflowd has some problems with the multi wan setup or it could be something completely different. So what could be the problem and how do I fix it?  ;)