Possible Wifi issues - can anyone help point me at the likely problem?

I’ve got Volumio 3.198 running on a Pi 4 with a Hifi berry DAC+ playing flac files from a CIFs share on a Synology NAS over wifi.
Most of the time it works great - but getting intermittent problems where the music will stop for a few minutes - sometimes just resuming, othertimes it will start to stutter for a few more minutes before recovering. It usually does recover.

I’ve been tailing the log while this happens and also running vmstat. vmstat shows the IO-wait going through the roof. The log at the time when the music stops playing just says Error: Error.

Here’s a link to a gist of one log:

The music stopped playing at 16:11:14

Lots of messages kicking about regarding wlan0 - is this a problem with wifi dropping out?

Weird thing it that I am connected from another machine via SSH and it doesn’t seem to miss a beat (vmstat 1 is outputting a line every 1 second)

If anyone knowledgeable could point me at the likely culprit I’d be very grateful!

PS. not in this log, but other times I get the following error close after the “Error: error” entries

volumio kernel: CIFS: VFS: \\disks has not responded in 180 seconds. Reconnecting...

It isn’t the drive/s in your NAS going into sleep mode or similar is it?

Possibly - I wondered about that.
I had the HDD hibernation set at 10 mins on the NAS and have moved it to 30 mins without much change. If I’m actively playing an album, is it possible that enough of it is cached to cause 30 min inactivity? I guess I need to turn hibernation off for a spell to rule it out though - thanks for the reply!