This is a spoiler in a list. You can't see the number unless you hover the spoiler.
- Numbering continues as expected.
The issue can be reproduced multiple times in a single list.
It even holds when a list item consists of multiple paragraphs.
- The issue holds in unordered lists as well.
This can be seen here.
The number/bullet is not hidden when the spoiler is not the first part of the list item.