Ever since we did the latest firmware update (about 2 weeks ago) the Wifi has been very spotty in a number of ways.  We are using it in a standard router mode, 3 deco boxes, one hooked directly up to the modem.  I verified that it is not requesting another update and that there aren't service interuptions from the ISP (comcast).  I have had the M5's for about 2 years and they've worked great until now.

Since the update: 

1. Overall download speed has been cut drastically.  I usualy get ~800Mb down.  The deco is saying after a speed test that I'm still getting that, but when I run a speed test on any of my devices, it's closer to ~50Mb down.  I've come to realize the speed test on the deco app is showing what they are getting from the modem, not what they are sending to devices.
2. Several of my devices are not able to connect. My HP printer and Ring doorbell can't seem to find the network. It doesn't show up in the list of availible networks even when I have devices right next to them connected to it.  I tried adding the network manually and that also does not work.  Fast Roaming is disabled and these devices did connect before the update.  I was able to successfully hook the printer up using a ethernet cable to one of the deco's, but it's not ideal.
3. Intermitantly, other devices can't connect to the network, like laptops and the Xbox.  Usually this goes away in about 30 minutes and they can connect again.   Seems to be related to above as the devices cannot find the network even though the light is green on the deco.
4. Randomly the deco seems to shut down.  The main deco attached to the modem will shut down - the light will turn red even though the modem shows all green. It does restart after a few minutes.

Overall this is giving us a lot of headachs as my family works from home.