NetFlow on Tunnel interface

NetFlow on Tunnel interface

Hello,

I have network with Cisco DMVPN with Hub and Spoke router, in brach office I have spoke router with Tunnel interface that receive traffic, I apply "ip flow monitor nf-monitor input" on LAN intraface in my case G0/1.10, in auto on NetFlow I see upload traffic from G0/1.10 to Tunnel, but I can't see download traffic from Tunnel to G0/1.10, so I apply on Tunnel "ip flow monitor nf-monitor input" but same before....
In this state I can see only one direction, see that traffic inbound on Tunnel can't see with netflow. maybe problem with ipsec crypto ?? inboud traffic on Tunnel is protect by ipsec.

Have you some idea ? becouse in this way I lost one direction completely

Thanks

M.