  Interferometry is a vital tool for studying fundamental features in the
quantum Hall effect (QHE). For instance, Aharonov-Bohm (AB) interference in a
quantum Hall interferometer can probe the wave-particle duality of electrons
and quasiparticles. Here, we report an unusual AB interference in a quantum
Hall Fabry-P\'erot interferometer (FPI), whose Coulomb interactions were
suppressed with a grounded drain in the interior bulk of the FPI. In a
descending filling factor from $\nu =3$ to $\nu\approx5/3$, the magnetic field
periodicity, which corresponded to a single 'flux quantum,' agreed accurately
with the enclosed area of the FPI. However, in the filling range,
$\nu\approx5/3$ to ${\nu}=1$, the field periodicity increased markedly, apriori
suggesting a drastic shrinkage of the AB area. Moreover, the modulation gate
voltage periodicity decreased abruptly at this range. We attribute these
unexpected observations to a ubiquitous edge reconstruction, leading to
dynamical area changing with the field and a modified modulation gate-edge
capacitance. These results are reproducible and support future interference
experiments with a QHE-FPI.
