Sorry I’ve been flat out with other things, the other devices have always been set to the Flexy’s lan IP address for the Gateway. I did notice that the DNS server was actually set to the same I.P address so I updated these to be 220.127.116.11.
Further to this I visited site and replaced the modem expansion card and installed the high gain antenna to try and improve the signal quality it was ranging between 13 - 16 and now 15 - 21. This still did not resolve the issue.
My next point of call was to reduce the amount of data being sent through the EWON, which meant disabling one Citect Server and comms to MindSphere. Since I have done this the Flexy has been running for 6 days with no issue (Fingers Crossed), I have since re enabled the Citect Server and MindSphere communications. I will keep an eye on it for now, but I belive it is due to the poor 4G network on site and the data the is being pushed through the m2m network.