Business relationships resemble love relationships in that trust is imperative inside that relationship. Ask yourself, is this a common pattern that you have always seen with this partner, which you have chosen to ignore? Is it a recent development which could be connected to some personal issues he/she is going through? Finally, is this a very rare hiccup that has occurred but you have always been able to count on this partner in the past. Analyzing these three perspectives could help you to decide how to proceed from here, but do also be aware, if something underlined issue is brewing between you and the partner or this partner and someone else, he/she could be using a passive-aggressive behavior designed to sabotage the project in order to humiliate someone in the company. Try to explore as many perspectives as you can...keep a journal of your thoughts and possible solutions. All the best