VPN Tunnel Crashes

Hello, my question is regarding VPN, I have 2 locations connected together via router to router VPN, Im using 2 Linksys RV082 routers, they have worked for few months, but just recently my VPN tunel just crashes every half hour, I went over the configuration many times, Im sure that is correct, so now Im suspecting something in my network is causing the tunnel to crash, I need some advice on what else could I check, what els could cause the tinnel to fail,,
thanks