There was indeed a delay of 6 months in the starting of the work but I don't think all the blame can be put at the feet of the builders. Contracts were slow in the signing, in part due to the Spanish Governments slow privatisation of Aena, which held up funding and the fine tuning of the plans and drawings.
The work for the new taxiway and stands was only put out to tender in March this year so the 4th part of the project has yet to start.
Whitemountain, who are the contractors for the CTA always strikes me that they are under staffed as they seem to have next to no workers on site and that if they doubled their meager workforce the CTA could have been finished by now seeing that work started last summer.
By contrast the contractor building the multistory car park always seems to have 4 times the workforce of Whitemountain, as their site is always a hive of activity and it shows with the speed of their building work.
As for the contractor building the terminal extension they arrived in January and after working on the old bus station for 7 months they have yet to start putting up the framework of the extension.