Hi @more SW problems 

Welcome to the Sonos Community! And, apologies for the delay.

Error 913 typically means that Sonos has refused the connection due to finding it to be SMBv1, rather than a later version (Sonos S2 only supports SMBv2/3). It may also be a mis-reported folder permissions issue.

I recommend a read of the following helpful thread on how to fix it:

I hope this helps.

more vague referrals that avoid answering why the software is so cruddy and how to resolve it

There is no doubt in my mind that the Sonos apps are the very worst apps I have EVER used, and especially the worst of any for which I paid via buying Sonos speakers.