LAN to LAN VPN Disconnecting

I just want to start off by saying my knowledge of a Mikrotik is very limited.

We have a scenario where we have a LAN to LAN VPN, Mikrotik one side, WatchGuard the other however recently it has intermittently disconnecting. The log shows the following.

phase1 negotiation failed due to time up local-end-ip[500]<=>remote-end-ip[500]

Usually it will usually reconnect, eventually, but occasionally we have to reboot the Mikrotik. We need this tunnel to be as constant and stable as possible. There are several VPNs of a similar nature going to the WatchGuard though usually Drayteks which are all stable, so I believe the problem to be somewhere on the Mikrotik. The two internet connections themselves do not lose any packets when the tunnel drops.

Firewall filter rules

Flags: X - disabled, I - invalid, D - dynamic 

 0    ;;; Accept ICMP

      chain=input action=accept protocol=icmp log=no log-prefix="" 

 1 XI  chain=input action=accept protocol=tcp dst-port=7746 log=no 

      log-prefix="" 

 2    chain=output action=reject reject-with=icmp-network-unreachable 

      protocol=tcp dst-address=redactedwanip log=no log-prefix="" 

 3    chain=output action=reject reject-with=icmp-network-unreachable 

      protocol=tcp dst-address=redactedwanip log=no log-prefix="" 

 4 XI  chain=input action=accept protocol=tcp dst-port=7746 log=no 

      log-prefix="" 

 5 XI  chain=input action=accept protocol=tcp dst-port=7746 log=no 

      log-prefix="" 

 6    ;;; Accept established related

      chain=input action=accept connection-state=established,related 

      log=no log-prefix="" 

 7    ;;; Accept Established Related

      chain=forward action=accept connection-state=established,related 

      log=no log-prefix="" 

 8    ;;; Accept remote access

      chain=input action=accept protocol=tcp 

      src-address-list=RemoteAccess in-interface=ether1 

      dst-port=88,8022,8443,8291 log=no log-prefix="" 

 9    chain=input action=accept protocol=udp src-port=500 log=no 

      log-prefix="" 

10    chain=input action=accept protocol=ipsec-esp log=no log-prefix="" 

11    chain=input action=accept protocol=ipsec-ah log=no log-prefix="" 

12    ;;; Allow Remote Server Access to 192.168.51.0/24 Network

      chain=forward action=accept src-address=10.0.1.20 

      dst-address=192.168.51.0/24 log=no log-prefix="" 

13    ;;; Allow Remote Server Access to 172.16.32.0/20 Network

      chain=forward action=accept src-address=10.0.1.20 

      dst-address=172.16.32.0/20 log=no log-prefix="" 

14    ;;; Allow Remote Server Access to 172.16.32.0/20 Network

      chain=forward action=accept src-address=10.0.1.20 

      dst-address=192.168.37.0/24 log=no log-prefix="" 

15    ;;; Drop all other input

      chain=input action=drop in-interface=ether1 log=no log-prefix="" 

16    ;;; Drop invalid

      chain=forward action=drop connection-state=invalid log=no 

      log-prefix="" 

17    ;;; Drop All Forwarding Un-wanted

      chain=forward action=drop in-interface=ether1 log=no log-prefix=""

NAT rules

Flags: X - disabled, I - invalid, D - dynamic 

 0    chain=srcnat action=accept src-address=172.16.32.0/20 

      dst-address=10.0.1.20 log=no log-prefix=""  

 1    chain=srcnat action=accept src-address=192.168.51.0/24 

      dst-address=10.0.1.20 log=no log-prefix="" 

 2    chain=srcnat action=accept src-address=192.168.37.0/24 

      dst-address=10.0.1.20 log=no log-prefix="" 

 3    ;;; Masquerade NAT

      chain=srcnat action=masquerade out-interface=ether1 log=no 

      log-prefix=""

Any ideas are welcomed. I find it puzzling as there have been no configuration changes on either end yet this was working perfectly until 2 days ago.