I don't think mine is tempeature related now that I think about it. I was almost convinced it was due to it happening most of the time when I left the unit in the car. But about a week ago, I had the empeg at my desk all day playing. At the end of the day, I packed it up in it's case, went outside to mild weather, and plugged it in. And it had the dimmer problem.

And earlier I said I would see what happens when daytime brightness is set to 90%, but I just realised I have also seen the problem when I haven't turned on my headlights. Most mornings I don't since it's bright enough, and it has happened in the morning as well.