Contourm works with some contour intervals but not others

In Matlab R2017a, contourm is behaving strangely -- given a set of plotting levels, it works when plotting some arrays but not others, even when those arrays differ only numerically. When it fails, I get an error using adjustPolarVertices-->"n polar vertices: too many". I have included an example of this puzzling behavior in the attached code. Adjusting the plotting levels to avoid this issue does sometimes work, but only sporadically and unpredictably.