SampleAndy, I'm - occasionally - having the same problem as you with the light and cover, though I don't have the official cover. I have noticed that the 'lights off but still showing text and not screensaver' problem occurs when I do the following:
- close the cover but open it almost immediately (the screen flashes when I do this, as if it was just bringing up the screensaver, but couldn't because I already opened the cover)
- close the cover and it doesn't line up perfectly with the sensor. I usually check this by gently peering under the cover at the top of the cover. Then I check the sides of the cover to see if they align perfectly, peer inside again, and if the sides are in place, the screen shows the screensaver.
Unfortunately, only restarting the Kindle, or using the physical button to unlock seems to help this problem.