After a week of intense research :), I finally found the data leak, and it has nothing to do with the MR600. I had a VLAN configured as a GUEST Network, our Home Office computers are connected to...

@Sunshine The MR600 is connected to the Edgeroute (Edgerouter 4 from Ubiquiti). The edgerouter is configured to use the MR600 only as failover (the logs show that it was not used, so no traffic...

I am using the MR600 as a failover internet connection. There is nothing connected to it but it manages to consume more than 5GB a day !!! It is an upgrade from the MR6400 that I was using before ......