Most often, delays are caused by network issues, between your controller and router, or the router and the speakers. I’d certainly check the wifi interference FAQ, as well as performing a Sonos network refresh, by unplugging your Sonos devices from power (or powering them off, if battery connected), and rebooting your router. Once the router has recovered, power back on your Sonos devices. This will give them both a fresh IP address, as well as a refresh of the Sonos OS. Finally, check your system for updates, in case there are any that need to be applied.

For what it’s worth, fixing IP addresses does the same thing, more permanently, as the network refresh. Never, IMHO, a bad idea. 

Note: If the above procedure suggested by ​@Airgetlam works, then reserving IP addresses will keep it from happening again. 

Thanks everyone. This is really helpful!