Perhaps this is a known issue. You can't put a codeblock directly after a list, even separated with line breaks. It came up in this question, where I finally just added a colon between the list and codeblock so that it would look right.
Here's a list:
- First line
This should be a code block, check the markdown!
(there needs to be at least one normal character in this line, or the next codeblock won't render either. Line breaks don't do it)
This is also a codeblock
But there are some good workarounds in those answers. My preference is to use
or a blank html comment
as a separator.