As a guess, it seems like some sort of wifi interference. There isn’t anything in the Sonos software, either S1 or S2 that would cause that.

It is entirely possible that this interference is coming from outside your network, especially given the timing. In addition to all of the potential solutions in the linked FAQ, I’d also consider changing either your Wi-Fi channel, or the SonosNet channel that your speakers are connected to. 

I agree with Bruce.  Purely for diagnostic purposes you could try changing your router’s wireless channel and see if the problem persists.

(Although before that….. do you currently have a Sonos device wired to your router, e.g. a speker or Bridge?)

Yes, I have a bridge.

While BRIDGE power supplies are known to be failure points, it would be unusual for one to fail on a schedule like you’ve described. However, as another test, try wiring an Ethernet cable directly to a Sonos speaker, and power down the BRIDGE, and see if the behaviour continues. 

Unfortunately I can wired the speaker they are 14 feet on the walls and far from the bridge.

Any other sugestions?

While they’re showing up in the controller, add your network information to the controller, then try powering down the BRIDGE. 

More reading at the wired and wireless modes FAQ.

There is no real guaranty this will work, however, given the 4 to 8 PM periodicity of your issue. I’d be betting on some external source of wifi interference , as I’d stated previously. 

Thank you.

I will definately give a try.