I can't seem to pinpoint the cause

common/debugging/region_checksum.cpp

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+/* Copyright: (c) Kayne Ruse 2013-2015
+ * 
+ * This software is provided 'as-is', without any express or implied
+ * warranty. In no event will the authors be held liable for any damages
+ * arising from the use of this software.
+ * 
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ * 
+ * 1. The origin of this software must not be misrepresented; you must not
+ * claim that you wrote the original software. If you use this software
+ * in a product, an acknowledgment in the product documentation would be
+ * appreciated but is not required.
+ * 
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ * misrepresented as being the original software.
+ * 
+ * 3. This notice may not be removed or altered from any source
+ * distribution.
+*/
+#include "region_checksum.hpp"
+
+int debugRegionSum(Region* const region) {
+	int sum = 0;
+	for(int i = 0; i < REGION_WIDTH; i++) {
+		for (int j = 0; j < REGION_HEIGHT; j++) {
+			for (int k = 0; k < REGION_DEPTH; k++) {
+				sum += region->GetTile(i, j, k);
+			}
+		}
+	}
+	return sum;
+}