Flows from Internet to WAN interface are missing in Insight

[abraxxa]

Flows from Internet to WAN interface are missing in Insight, for example flows from an Internet host to haProxy listening on the WAN interface.
The connection from haProxy to the inside host via the LAN interface are there but of course only show the LAN interface IP.
My Netflow configuration is to listen on all interfaces (including WAN and LAN) and the Internet facing 'WAN' interface is the only configured under 'WAN interfaces'.
I guess the IPv4 double counting prevention for NAT swallows those.