Vim does not seem to correctly react at a dash symbol in YAML files therefore breaking the format.
For example I have a block which should look like this:
Install this plugin:
https://github.com/chase/vim-ansible-yaml
It is made with Ansible in mind, but in theory it will work with all kinds of YAML files. You will have to :set filetype=ansible unfortunately, if you are not working with ansible related files.