The code macro is not rendering correctly if multiple code blocks on the same page are set to different themes.
I have tested this on 4.3.7 and 5.0, I have also changed the Space Theme between "Global Look and Feel" and "Documentation" same issue.

the attached screenshots show the 2 code blocks where set to RDark which renders correctly and then I changed the top code block to default and it still rendered RDark.

Thanks
Conor