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When the timeline is locked then you will not observe any progress in time, and the simulation is “pinned” to the current frame. This means that the simulation is running, but frames are not incremented – the simulation is performed at a single frame, e.g. 0 or 50. As a side effect, animation data will not be evaluated. In order to unlock the timeline, stop the simulation with a click on “Simulate”, and click on the button again.
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