  The accelerated electrons during solar flares produce radio bursts and
nonthermal X-ray signatures. The quasi-periodic pulsations (QPPs) and fine
structures in spatial-spectral-temporal space in radio bursts depend on the
emission mechanism and the local conditions, such as magnetic fields, electron
density, and pitch angle distribution. Radio burst observations with high
frequency-time resolution imaging provide excellent diagnostics. In converging
magnetic field geometries, the radio bursts can be produced via the
electron-cyclotron maser (ECM). Recently, using observations made by the Karl
G. Jansky Very Large Array (VLA) at 1--2 GHz, \cite{Yu2023} reported a
discovery of long-lasting auroral-like radio bursts persistent over a sunspot
and interpreted them as ECM-generated emission. Here, we investigate the
detailed second and sub-second temporal variability of this continuous ECM
source. We study the association of 5-second period QPPs with a concurrent GOES
C1.5-class flare, utilizing VLA's imaging spectroscopy capability with an
extremely high temporal resolution (50 ms). We use the density and magnetic
field extrapolation model to constrain the ECM emission to the second harmonic
o-mode. Using the delay of QPPs from X-ray emission times, combined with X-ray
spectroscopy and magnetic extrapolation, we constrain the energies and pitch
angles of the ECM-emitting electrons to $\approx$4-8 keV and $>26^{\circ}$. Our
analysis shows that the loss-cone diffusion continuously fuels the ECM via
Coulomb collisions and magnetic turbulence between a 5 Mm--100 Mm length scale.
We conclude that the QPP occurs via the Lotka-Volterra system, where the
electron from solar flares saturates the continuously operating ECM and causes
temporary oscillations.
