Despite joining the EU 14 years ago, Bulgaria and Romania are still not part of the Schengen area. The wiki article has the following timeline:
On 1 August 2018, Bulgaria and Romania gained full access to the Schengen Information System. Moreover, "the final political decision whether the two countries can become part of the Schengen area and stop systematic border checks with neighbouring EU countries must be taken unanimously by all sides of the European Council." On 11 December 2018, the European Parliament voted for the resolution in favour of accepting both countries, requiring the Council of the European Union to "act swiftly" on the matter.
What is currently stalling the acceptance of these countries into the Schengen area? I'm interested in both official and informal reasons for the delay.