  The symmetron is a dark energy and dark matter candidate that forms
topological defects in the late-time universe and holds promise to resolve some
of the cosmological tensions. We perform high resolution simulations of the
dynamical and non-linear (a)symmetron using the recently developed relativistic
N-body code asevolution. By extensively testing the temporal and spatial
convergence of domain decompositioning and domain wall stability, we find
criteria and physical intuition for the convergence. We apply the resolution
criteria to run five high resolution, $1280^3$ grids and 500 Mpc/h boxsize,
simulations of the (a)symmetron and consider the behaviour of the scalar field
and the domain walls in each scenario. We find the effect on the matter power
spectra, the halo mass function and observables computed over the past
lightcone of an observer such as the integrated Sachs-Wolfe and non-linear
Rees-Sciama effect (ISW-RS) and the lensing, compared to LCDM. We show local
oscillations of the fifth force strength and the formation of planar structures
in the density field. The dynamics of the field is visualised in animations
with high resolution in time. The simulation code is made publicly available.
