Sonos systems are great. They're flexible, compatible with a wide range of consumer music services, and easy to setup. However, they have some shortcomings that can bite you hard in a professional environment requiring flawless 24/7 operation.
At the heart of these shortcomings is usually the reliance on WiFi for audio distributions.
WiFi technology is not designed for realtime distribution of audio. Realtime distribution of audio requires the underlying network to deliver audio packets from source to destination…
… very quickly. Each audio packet typically has only a few tens of milliseconds to reach its destination.
… very often. Packets are typically sent at a high frequency, which can reach hundreds of packets per second.
… all the time.
If just a single packet arrives late just once, it leads to an audible audio crack or gap.
Wireless networks do not provide any such guarantee. At its core, the technology cannot allow it. Radio signals get lost or absorbed. Noise levels fluctuate. Noisy neighbours come and go as wireless devices nearby get turned on and off. Even a weather radar miles away could activate and force your wireless access point into changing channel, thus interrupting audio transmission (see DFS).
What the technology does guarantee is a best effort approach: packets which haven't reached their destination are retransmitted a few times before giving up. Sadly, this does cut it for realtime audio distribution.
The bottom line is this:
Sonos systems require a flawless local network. If your WiFi network has even the slightest hiccup, it will translate into an audible audio gap.
Notes:
Wireless performance & reliability issues may go undetected if the network is mostly used for web browsing, email, Youtube, etc. For these use cases, a dropped/late packet will at worst translate into a web page taking a bit longer to load than usual, or a Youtube video stalling for a bit. The impact is almost un-noticeable.
The Sonos mobile application offers natively integrated music services (e.g. Spotify, Tidal) that typically work quite reliably. These services benefit from strong buffering that can absorb minutes-long network interruptions. Sadly, this buffering logic is disabled when plugging a non-Sonos appliance through a Sonos Port/Connect. This impacts any 3rd party audio source, whether it's a Spectre player, a DJ turntable, a PC/laptop, or anything else.
Some remedies can be applied to reduce the chance of audio cracks/gaps occurring.
Switch to wired distribution
WiFi is not suited for reliable 24/7 realtime audio distribution. If possible, the best solution is to connect all your Sonos appliances with Ethernet cables.
Increase buffering
Increasing the audio buffer of your Sonos system will introduce a slight audio delay but will make the system much more resilient to small network interruptions. To increase the audio buffering of your Sonos devices, head into your Sonos mobile app. Select each Sonos product in your system with a Line-in connector, head into their settings, and look for the "Line-In" and "Audio Delay" parameters. Raise Audio Delay to the maximum value allowed.
Enable audio compression
Enabling compression of audio will reduce the bandwidth required for transmission over your network, improving reliability somehow at the cost of some audio quality. Enabling it should be a last resort solution.
Let your WiFi router/AP automatically select its radio channel
WiFi networks operate over a specific radio frequency range (e.g. channel 118: 5570–5610MHz). If neighbouring wireless devices operate on the range, the performance and reliablity of your own network will be negatively impacted. Most WiFi routers and access points do a good job automatically picking a less crowded radio channel. If your WiFi router or access point is manually set to a specific channel, you should either really know what you are doing or re-enable automatic channel selection.
Relocate your speakers and/or WiFi router/AP
The weakest link in your WiFi system is likely to be the wireless connection between your speakers and your WiFi router or access point. If possible, move them to bring them closer to each other.
Use a dedicated wireless network for your Sonos system
The more wireless devices talk to each other on a network, the lower will be its performance and stability. If possible, use a dedicated network for your Sonos system.
Reduce channel width
WiFi networks can operate over multiple channels at the same time. This increases bandwidth, but increases the risk of overlapping with a "noisy neighbour". Reduce the channel width to improve the reliability of your network.
Avoid DFS channels
DFS channels are radio ranges that can be at any time reclaimed by military or civil radio infrastructures (e.g. weather radars) that will take priority over your own devices. On activation, these radio emitters will remotely disable your own network and force it into a lengthy channel renegotiation that can take tens of seconds.
Remove source of radio interference
Some appliances emit radio signals in the same frequency range as your WiFi network, and may negatively impact it. Examples include cordless/DECT phones, baby monitors, security cameras, microwaves, drones, etc.
Replace your WiFi router / access point
Some WiFi routers or access points are just more robust and reliable than others. Investing in high quality hardware (e.g. Cisco, Mikrotik, etc) may pay off.
Ask a professional
Wireless systems are more complex than they appear on the surface. This note only scratches the surface of the various ways a network can misbehave. In doubt, ask a professional.