Hi Anders,
In the SampleWithTimeIndex Prototype, the control for the Start parameter is !MarkAttack and it interacts with the values for !MarkEndAttack and !MarkLoopBegin. In other words, the start of the attack can't be greater than the value for the end of the attack or the start of the loop.
If you set Start, EndAttack, and StartLoop to !Start. And EndLoop, StartRelease, and End to !End, then the start point will be updated each time Gate becomes true.
I would also uncheck Looping and set ForwardBackward to 0.