Tinc clients behind a NAT, tunnels get unstable

[Marcus Schopen]

Hi,

I'm running some tinc clients behind a NAT (masquerading, Cisco Router)
connecting to a host outside on a public IP in a different network. The
tunnels get unstable every few minutes and I see packet loss when
pinging the clients on their internal tunnel IPs from the host side. 
 Before putting the tinc clients behind the NAT they were running on
public IPs too (clients and host in different networks) and the tunnels
were rock stable without any problems. As a workaround(?) I added
"TCPOnly = yes" [1] to the host's config file and since then all tunnels
seem to work stable again, but I can't explain this to me as the NAT
should handle UDP connections. Any ideas?

Cheers,
Marcus

[1] http://tinc-vpn.org/documentation/Solving-problems.html