Is there a wired Sonos component elsewhere? If so, and the system’s therefore in SonosNet mode, you can run a cable as suggested. It will be used in preference to the 5GHz wireless.

Yes, I have a wired Boost as only wired component.

I am going to put a cable between the Sub and Playbase,

Thanks for the quick and clear reply.

Note that direct wiring will only mitigate wireless interference dropouts, it will do nothing regarding other causes of dropouts, such as duplicate IP addresses.

It can help in some situations, but is not a silver bullet. 

Thanks for the addition. As far as I know I do not have duplicate IP adresses, but I will keep this in mind.

My idea is that the channel used by the system (5.7 Mhz) is a DFS channel and maybe the system does not handle this very well.

Its just speculation, but if a cable can prevent the disconnects, then I will do this.

The 5GHz channel is dynamic. The Playbase will select a channel automatically in order to avoid congestion and interference, and it can change very quickly, whilst the system is playing. Sonos also uses the DFS channels as required. 

I am inspecting the channel for 5Ghz often, and have never seen anything else then 5700. But maybe I looked at the wrong moments.