That suppliers sometimes spoil the best project planning is probably nothing unusual. I also often experienced a comprehension of project management at subs that did not even allow provisions to plan.
From my long experience in project reviews and auditing I have developed a method that enables to assess and validate suppliers’ project management capabilities already at solicitation. Thus your procurement could incorporate process quality ensurance measures or requirements such as expediting and/or recommendations to Project Management recruitment in case of provisions risk into the procurement documents of an upcoming project.
Would you like to enlarge upon the topic with me? Your feedback is welcome !