Hi all. First of all, my apologies for this necessarily lengthy post.

I really don't know whether to love or hate my Squeezebox set-up. Its absolutely great when working. A nightmare when it glitches.
I suspect the glitches are more to do with my network rather than Logitech's h/w & s/w, but who knows, I don't.

My Duet had recently started to fail to connect, as it does from time to time. This time however, the previously reliable techniques of re-establishing my all-wireless set-up using
a temporary Ethernet connection, resetting router, flushing cache, etc, etc, all failed to rectify the problem.
After wasting hours of my life yet again, I managed to get the Duet up and running (visible in LMS and with bright white light on front of the Duet) but all I got was noise
akin to a FAX machine, so I assumed the Duet hardware or power supply was expiring.

So, I decided to buy a secondhand Duet via eBay. I was able to set this up at first attempt and it worked fine. Great, I thought, the culprit was my old Duet and/or its power adaptor.

However!, after working fine for a couple of weeks, the replacement Duet is now doing the same as the old Duet: i.e. failing to connect, or connecting but issuing the FAX-like screeching when it is willing to stream.

BTW I have a Squeezebox Boom which is totally unnaffected by these issues - it works a treat, never failing to re-establish a connection when powered down, or following a power cut to router, etc.
(another reason to sometimes hate the Duet!).

Previously, at least the Duet's lights were consistent. When my old Duet failed to connect that last time, its coloured lights no longer appeared to behave in the usual way (blue, dull white, bright white and so forth).
The evening before, I noticed the Duet's light was bright white even though LMS was not running.
When the replacement Duet also started to fail, again its lights have not behaved in the usual way - it was cycling between flashing red, through to dull/bright white. I havent seen a blue or green at all.

To further confuse me, and finally prompting me to post this cry for help, after powering everything down and starting afresh (with the replacement Duet), I once again set up the controller to re-establish
a WiFi network connection, then used it to configure the Duet (temporarily Ethernet connected to Laptop hosting LMS & music libraries).
Controller, LMS and Squeezer all seem happy: they see the Duet and can be used to command the Duet to play music (with Ethernet cable now disconnected), yet the Duet itself is still flashing red (waiting to be set up?).

How can the Duet be actively streaming (either via Ethernet or WiFi) while flashing Red??

My set-up is as follows:

Windows 10 laptop, running LMS 7.7.5, starting automatically at Login (during the above attempts to rectify the problem, I updated to 7.7.6 but it had no effect).
The laptop is also host to my media libraries.
Squeezer Android app version 1.5.1
Controller firmware version 7.7.3 r16662. Current IP address 192.168.0.14
Duet firmware version 77 , signal strength 85%. Current IP address 192.168.0.34
Boom firmware version 57, signal strength 75%. Current IP address 192.168.0.27
All connected via WiFi using dynamic IPs via DHCP.
Router (Virgin Media Hub 3.0 - a Broadcom 802.11n Network Adapter) running with default config, e.g. no reserved DHCP IPs etc.
I don't know how to check the range of IP addresses available on DHCP. I've assumed its more than the current utilisation range, or could it be 32???
Can the router be flushed of used IP addresses? - I'm sure I haven't 34 devices in the house.

I haven't changed any router settings. My provider (VM) might automatically upload firmware updates. Could that upset my set up?
I haven't changed my s/w firewall settings either (AVG Internet Security).

Is there a network set-up that would avoid these presumed network glitches?
Should I attempt to use static IP addresses, or reserved DHCP IP addresses?

Any ideas gratefully received.
Apologies for all the questions.
Many thanks.