Hi Dazzerbone, thank you for your post, I don't feel lonely anymore!
I have exactly the same problem than you since a few days. I was controlling two LightWaveRF dimmer switches through an echo group and dimming is no longer working. I have tried to remove groups, devices, skill...I have not managed to make it work again. I am still able to turn the lights on/off but when I use the command "dim" or "set" I am either asked to specify the name of the device (I have a very clean list there can't be a missunderstanding) or I am told that this action is not working on device "all lights".
To reply to tuicemen, I have checked the history requests to Alexa and she definitively understand each word I say.
Are we only two to face this issue? Any idea would be welcome to fix this!