Inner frame was a bit too large (nonsymmetrical).

beamerthemelumc.sty

@@ -81,7 +81,7 @@
 \newenvironment{pframe}{
   \begin{frame}[fragile, environment=pframe]
     \frametitle{\insertsubsection}
-    \begin{minipage}[t][1.03\textheight]{1.03\textwidth}
+    \begin{minipage}[t][1.03\textheight]{\textwidth}
 }{
     \end{minipage}
   \end{frame}