That log is not available to us users. Immediately after one of these events you’ll need to submit a diagnostic and work with SONOS phone support. Note that a speaker will protect itself by reducing Volume or shutting down if you are playing too loud.

Is it turning down gradually? (i.e. the moment you turn it up it starts turning itself down until it hits 0)
Is it turning down incrementally? (i.e. every time you turn it up it turns down a certain amount?)
Is it turning down periodically to a *fixed* level? (e.g. it drops to 15% on its own?)

If it’s the first 2 - probably a button issue. If it’s the last one, it’s most likely an amp fault (i.e. internal fault), temp fault (sensor thinks the component is getting too hot) or CPU fault. Volume will clamp in these scenarios as a protective feature to avoid damage.

As the poster above said, take a diagnostic *when the problem is happening* (diagnostics are like a snapshot, so we get about 20 minutes of data prior to when you submit it), then contact support with the confirmation number. If it’s a fault like I described, these are usually very easy to detect provided you capture the behavior in your diag.