  We report VLBA observations of 22 GHz H$_{2}$O and 43 GHz SiO masers toward
the Mira variable RR Aql. By fitting the SiO maser emission to a circular ring,
we estimate the absolute stellar position of RR Aql and find agreement with
Gaia astrometry to within the joint uncertainty of $\approx1$ mas. Using the
maser astrometry we measure a stellar parallax of 2.44 $\pm$ 0.07 mas,
corresponding to a distance of 410$^{+12}_{-11}$ pc. The maser parallax
deviates significantly from the Gaia EDR3 parallax of 1.95 $\pm$ 0.11 mas,
indicating a $3.8\sigma$ tension between radio and optical measurements. This
tension is most likely caused by optical photo-center variations limiting the
Gaia astrometric accuracy for this Mira variable. Combining infrared magnitudes
with parallaxes for RR Aql and other Miras, we fit a period-luminosity relation
using a Bayesian approach with MCMC sampling and a strong prior for the slope
of -3.60 $\pm$ 0.30 from the LMC. We find a $K$-band zero-point (defined at
logP(days) = 2.30) of -6.79 $\pm$ 0.15 mag using VLBI parallaxes and -7.08
$\pm$ 0.29 mag using Gaia parallaxes. The Gaia zero-point is statistically
consistent with the more accurate VLBI value.
