• Mark the starting point (date) for group of tasks - In this case we set the MS date by using the "start not earlier than" constraints, and set the MS to be the predecessor of the tasks. This works fine.
• Mark the completion (date) for group of tasks - In this case we define the tasks to be the predecessors of the MS, and let RTC calculate the MS date. In most cases this works fine, and the MS date is the shows the completion date of the last task. However, sometime a delay is shown (as can be seen in the below screenshot). This looks like a bug in RTC. 

More details:

• If we change the owner of the MS, then the calculated date is changed.
• We tried to give the MS higher rank, but this did not solve the problem.
• We plan to use MS to sync between different parts of the same plan, and also to sync between different teams. Hence Ms are of high importance.

What am I missing?

Thanks,
Raviv.