yields are strongly affected by cluster merging when two photons from a $\pi^0$ decay have a small opening angle and produce partially or fully overlapping showers, which cannot be reconstructed as two individual clusters in the EMCal. Cluster merging results in significant loss of $\pi^0$ reconstruction efficiency at high $p_T$. Due to the different segmentation and Moliere-radius [@Aphecetche:2003zr] the merging effect manifests itself differently in the PbSc and PbGl subsystems. In PbSc the merging starts at $p_T>12$ GeV/$c$, while in PbGl it starts only at $p_T>16$ GeV/$c$. Uncertainties on how well the simulations describe the merging effect result in corresponding uncertainties for the measured $\pi^0$ yields, increase with , reaching $\approx$20$\%$ in PbSc and $\approx$9$\%$ in PbGl at 20 GeV/$c$. Due to the four times heavier mass and larger $\gamma\gamma$ opening angle, the $\eta$ measurements will be influenced by cluster merging only at $p_T>50$ GeV/$c$, which is far beyond the $p_T$ range presented in this analysis. At low $p_T$ (below $\approx$5 GeV/$c$) the main uncertainty for $\pi^0$ and $\eta$ comes from the raw yield extraction due to relatively small $S/B$ ratios. This uncertainty is estimated as the maximum difference between raw yields obtained using different mass regions for mixed event 