@z33tec 

If the dropping continues to stay where the main Deco is you could try swapping the Ethernet cable being used from the Deco to the modem. If the modem is a cable modem log into its system logs to see if there may be any critical 3 or 4 errors that cause random internet drops.

@Tony 

That would make sense if I didn't continue to have a solid connection over wifi on the other 2 deco's as well as the hard wired devices on the switch that's plugged into the main Deco's eth port. If the cable was bad going to modem, it would impact all connectivity, not just wifi on the main node.

@z33tec 

I have the M9 Plus as well and was also having similiar issues. Internet kept randomly being disconnected which was traced to the main unit. I couldn't figure it out until the ethernet cable from main M9 unit to modem burnt out, which was only 6 months old at that point.

I figured it was a thermal issue.

All traffic has to go through the main unit whereas slave units only handle what is on that particular unit and it's really only passing information along. So the main unit has to not only handle all the traffic but also uses more CPU power. The main unit was significantly hotter than the slave units.

A couple things to try:

1) try raising the bottom of M9 off the table or platform. This is the only ventilation point for the M9. I put four small rubber legs onto my M9, raising it about an inch off the table.

2) You can try removing the top cover. The only ventilation point is on the bottom, as noted earlier, and hot air likes to rise so most of the heat is being trapped within the M9.

3) You can add heatsinks to the M9. The M9 from the factory uses three large, flat aluminum plates as heatsinks with thermal tape/pad for passive cooling. One on the top and the other two stacked on top of each other on the bottom. Adding more heatsinks, and/or going to a finned heatsink, will give more surface area for conductive (from the electrical components to the heat sink) and convective transfer (from the heatsink to air).

#1 reduced WiFi cutouts to about two or three times a week for me. This was not satisfactory for me and I went straight to #3. I removed the top cover, all three factory heatsinks and added larger passive CPU coolers as well as smaller units to both the top and bottom with a thermal pad/tape and smaller flat blocks acting as an intermediatary. I put this is back onto the M9 bottom plate with no top cover for now. It runs MUCH cooler to the touch now and I have not had any issues with dropping internet since. 

I found a small, cheap, old mini-ITX case from craigslist that I will be putting the M9 in (along with a switch and the modem) to prevent dust build up, clean up the table, and prevent touching but need to figure out how to get the antennas outside of the case first. 

Your issue is slightly different in that only the WiFi cuts out but I think 1 and 2 is worth a try before spending any $$$ either on heatsinks or a new system.

@z33tec 

I'm also experiencing problems with my wi-fi dropping several times daily. I had presumabley updated the firmware when I installed these units a few weeks ago, and the problem was immediate. My husband who lectures from home immediately dosconnected all but the main unit and we still have problems. My phone and computer drop and need to have the wifi pw entered almost every time. I'm not interested in having to do work-arounds for a product that should be user friendly and work out of the box for the regular person like me who isn't as tech savvy. If I installed it incorrectly could this be the problem?