If you configure a custom skin for a site (Different than the default) and you edit the site, you'll lose the configuration and the default will be shown.
Steps to reproduce (10.x for example, hard to reproduce in 11.x and Master because there is only 1 skin):
- Go to sites -> Find site with id "DAC-EDUCATION-DEPT1-SUBJ1-101" -> assign skin "default-horiz" -> save
- go to /portal/site/DAC-EDUCATION-DEPT1-SUBJ1-101 and check the skin "default-horiz" is configured (Miskatonic)
- Go to "site info" -> edit site information -> click continue -> Finish
- The default-horiz skin is lost.