This is something to do with element binding… Which we don’t have an ‘off switch’ for inside Dynamo (I don’t believe).
The second run is remembering the first run’s input and adding the Z value, for whatever reason, it does seem a little unexpected, but perhaps that’s because i don’t fully understand the binding process.
When you run through Player, there is no binding, so you don’t get that problem.
There is a post here and further link you might find useful: