Is there a bug in geom_boxplot ? When the box is very short, whiskers don't always extend correctly. In this image, the lower (unlike the upper) whisker fails to extend either to 1.5 times the IQR or to the farthest data point . . .
[PS: I also see the same apparent bug at https://ggplot2.tidyverse.org/reference/geom_boxplot.html is the "minivan" condition in the example that uses horizontally jittered data points. The upper whisker is supposed to extend either to the one point that's above the box or to 1.5 times the IQR. It does neither.]