How to fix IPSEC VPN getting down very frequently?

Hi,
I have multiple IPSEC VPN connection with my router RB100 V5.26. All of them are with CISCO router. One of my VPN is getting down very frequently. I can reach to the destination address very smoothly. The tunnel perform like a unidirectional tunnel. But the remote system can’t connect to my router. When I perform a restart on my router the tunnel comes up for few minutes and again goes down. I have different proposal, peers and policies for different VPN. I do not have any idea how to fix it. Please help

Bappy