IPFS dev here -- judging from a quick look, Scout uses NAT-PMP and UPnP for NAT traversal, so it basically has the same occasional NAT issues as everybody else in the P2P space. By the way, sometimes NAT issues are the fault of routers handed out by ISPs. The quality of these is often less than ideal.

(A pretty cool approach to circumventing NAT issues is a proper routed overlay network, which we plan to implement in libp2p soon: https://github.com/ipfs/notes/issues/143)