There's a couple of possibilities to consider. First is
Wifi Interference . Be sure to note that the PLAYBAR communicates with the SUB and surrounds on the 5Ghz channel, rather than the normal 2.4Ghz channel the rest of the Sonos system uses.
The other possibility is duplicate IP addresses, exposed when Sonos does a soft reboot of the speakers when they do a software update. Easiest way to fix this is to unplug your Sonos devices from power, then reboot the router. Once the router comes back up, plug in one of the Sonos devices. If you have one wired to the router with an ethernet cable, do that one first. Wait a minute for it to boot up fully, then move on to the next Sonos device, and plug that one in. Repeat this process for each of the rest of your Sonos.
A longer term way to address this particular issue is to assign all of your Sonos devices reserved / static IP addresses. Each router manufacturer seems to do this in a slightly different way, so you may need to pull out your router's manual.