MS Project Cannot Change Start Date (2007/2010/2013/2016)

Jumping Start Dates

Start date always jumps back to specific date in MS Project plan when you try to change it.
This is an issue I have not seen before, but to be honest it is a long time since I last touched a project plan.

Problem

Whenever I try to change Task 03 to something earlier then the 26th. The date is just resets to 26 without any explanation.

Reason
The reason is that there is a binding on the phases. Most likely with a lag of minus some days.

This binding forces the task to not being able to start earlier than the phase start.

Now this is somehow obvious, it becomes more comeplex if the task have an actual start date (if a team member have reported time on the task through Timesheet or MyTasks).

In this scenario the phase appear to start on the 23th. However, it actually starts on the 26th.
Now I cannot move new tasks within the phase before the original start date of the phase (the 26th).

This makes sense, but from the Gant Chart it is not very clear,

Solution
Well, if you understand the problem the solution is simple.
Remove the binding from the phases, In fact this is not a real binding anyway, because the task actually started at a time where it sould not be possible.

Or you can ask your team member to register his time at another date. This is of cause only a solution if the team member did not do the work at the reported date.