Thanks for the reply.
So as an example, my lounge has a combination of hue and osram bulbs, plus some smartthings outlets. They're all recognised by alexa as lights. There are also some other outlets that control the TV power, Hifi etc.
This has all been fine until the last couple of weeks. I could say 'alexa turn off the TV' or 'Alexa turn off the lights' and it would do as outlined.
Now however, intermittently, only with the lights, if I say 'alexa turn off the lights' or 'alexa, lights off' it responds with the message mentioned, that they're invalid commands for lights. Which of course, they're not.
The lounge group, contains the echo plus, the various lights and switches so the context element of not having to specify the group or room name applies.