In general in a correctly implemented fixed-step ODE solver method you have 3 sources for numerical errors:
the theoretical method truncation error,
the floating point error from evaluating the ODE function and composing the method step and
the error from accumulating the single updates of size $O(h)$ to the integration result of size $O(1)$.
So the total ...
I can share my perspective on this topic and can try to prove that the Leapfrog (velocity Verlet) is time-reversible, according to an appropriate definition of time reversibility (very nice property that increases this integration method's accuracy, alongside its $\Delta t^2$ convergence and symplecticity).
The idea behind Leapfrog:
Assume you have a system ...