Ok, so spending some time with the support from CISCO, we found a turnaround... which is not the best but it works. The problem for us seems to be coming from the fact that we use one WAN connected in PPPoE and the other one is in Static IP. Apparent...
I have the same exact issue and it doesn't look like anybody has found a proper solution?I use the two WAN connections with two different ISP (both of them being gigabyte speed). Once in a while (usually by night, so when the system is pretty idle), ...