Prior to updating my network from 1.4.9 to v1.5.1, my network was running flawlessly.
After updating my 3 Deco5v3 units to v1.5.1 firmware from v1.4.9, my network became completely unstable and was unusable.
The Decos would randomly drop off the network with a blinking red light. In response to this, I did a reset on each unit, then recreated the mesh network. This made no difference.
The WiFi and the connection between the Main Deco and the Cable Modem starting see ~20% packet loss as shown by PingPlotter.
Over 3 days, I tried various resets, change ethernet backhaul cables. Reboot the cable modem multiple times. Made each of the Decos the main Deco. And, none of these things helped.
Today, I used TFTP and restored v1.4.9 firmware back onto each Deco. I then reset each of the 3 Decos and recreated the network. After doing this the network was completely stable with no Decos dropping off. I was still randomly seeing ~15% packet loss over WiFi. As a result, I disabled Beam Forming, rebooted all Decos and the packet loss as completely stopped. The only way I can force any packet loss is to set PingPlotter to 1 second ping interval and then about every 10th ping will show loss.
This 1.5.1 firmware seems to definitely have issues!