192.168.3.1 doesn't know about 192.168.2.0, therefore it's trying to route the packet out over the Internet.
Couple of things to check:-
(1) If it works on the other routers without you having added a route then look at the RIP settings on the VPN at each end.
(2) Check you have the right subnets on the VPN - mistake I often make is assign the wrong subnet to the VPN, the connection still gets made and everything seems OK, but obviously it will never work.
(3) User separate logins for each VPN, not the same user name and password - the Draytek boxes get confused if you do this.
