Speed of Physics2D simulations are dependant on frameRate in Creator 3.5.2


We are using DistanceJoint2D to simulate a simple pendulum. We have observed that whenever the frame rate falls below a certain point on some devices, the physics simulations slow down significantly.

To be sure, we conducted an experiment by setting the fixedTimeStep and the game frameRate. We have observed that the physics simulation slows down when the frame rate falls below (1/fixedTimeStep).
For example if the frame rate is 29.99 fps and the physics fixedTimeStep is 1/15, then it works fine as long as the fps stays above 15 fps. But, if fixedTimeStep is set to 1/60, then the speed of physics simulation drops to almost half and if we further decrease the fixed time step to 1/120, the speed decrease to the quarter while the frame rate stays at approximately 30. This behaviour cannot be blamed on the computing power of the device because it works fine when fixedTimeStep is set to 1/120 and frame rate is set to 144.

How can we stabilise the physics behaviour in order to get the same results irrespective of the frame rate? Am I missing something?

Edit: The same behaviour is observed in Creator 5.6.0 also.