"More than one device" when using Alexa to set temps.

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Anyone else come across this? It's driving me mad!

I have smart thermostats in most rooms and I used to be able to say "Set the hall to 18 degrees" and that's what happened.

Now Alexa complains that "i found more than one device called 'hall'. Give them unique names and run discovery again".

When I log into Alexa.amazon.co.uk I can see multiple instances of all the thermostats so I remove them...and it works! Until I have to refresh the device list and then they all reappear and the problem returns.

Can anyone help with this please?