The layout engine of QwtPlot assumes, that the first major tick is at the left and the last one is at the right side of the scale. But in your code its the other way round.
I will think about how to fix this bug in Qwt ( manually generated ticks need to be ordered, after they have been passed with setScaleDiv).
In the meantime you could simply turn the order of your ticks.
Uwe
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