Using the gem scrivito_tabs_in_details in combination with this gem causes layout problems if Codemirror is not shown in the first visible tab. You have to click to make the codemirror editor appear and the styles are not assigned properly, as the line numbers collide with the source, for example.
It works if you enter as many lines as needed to make the codemirror scrollbar appear, though.
See this gif for details:

Gems:
scrivito_tabs_in_details 0.0.2
scrivito_codemirror_editor 1.0.0
cc @Dirk82