Actually, sometimes 40% seems to be okay, other times it shows my problem, and still other times, it shows the problem about halfway.

In the latter case, some of the off columns are lit and others are not, usually in clusters. Sometimes some of the columns flicker and some are lit. Sometimes all of the affected columns flicker.

There's obviously some threshold problem.

Also, there now seems to be no difference in brightness beween the 70%, 80%, 90%, and 100% settings. This may explain the perceived dimness this morning.