Description of the problem

The following command uses -Bnesw to plot 4 axes:

gmt basemap -R0/40/0/40 -JX4c/4c -Bnesw -Baf -png map

Use -Bn gives:

Use -Bs gives:

GMT may incorrectly interpret s as the secondary axis/annotation/label.

System information

• Operating system: macOS
• GMT version (gmt --version): 6.3.0_17131b2_2021.06.15