Communicating Concerns about the Collaboration
Almost everyone I know who collaborates extensively has some horror story about collaboration.
Person A was involved in a 3 person project with colleague B at his institution and colleague C elsewhere. A and B were actively working together on the project, but B was doing most of the communication with C. C got the idea that A was not contributing and "fired" A from the project. B, A's supervisor at work, failed to defend A, so his contribution was not acknowledged. Mistake: not making sure that his contributions were labeled as his throughout the work.
In a similar situation, D, E, and F worked together, developing a project loosely based on D's thesis. D left the company, and E and F published without D on the author list. Mistake: trusting the wrong people.
I collaborated for several years on one project, meeting weekly to discuss progress. My two collaborators found time to write many joint papers but never found time to integrate my part of the project with theirs so that we could write it up. Mistake: not speaking up about how important it was to my tenure case to get this work out.
The bottom line is that collaboration is a relationship, and not all relationships work out. Inevitably, some will crash and burn, and it is important to pick yourself up and walk away. Don't let yourself burn up with resentment. Eventually you will learn how to more reliably choose good collaborators. And when you do, it can be the most satisfying work that you have ever done.