diff --git a/MUNGA/ENTITY.cpp b/MUNGA/ENTITY.cpp
index af7c005..6ce16ec 100644
--- a/MUNGA/ENTITY.cpp
+++ b/MUNGA/ENTITY.cpp
@@ -435,6 +435,61 @@ void
 			//-----------------------
 			//
 			UpdateRecord *update = (UpdateRecord*)record;
+
+			//
+			// RP412CAMLOG: how hard does an arriving update MOVE this
+			// entity, and how often?
+			//
+			// Between updates a replicant is dead-reckoned from
+			// updateOrigin over (lastPerformance - lastUpdate). When the
+			// next one lands the basis is replaced, so the drawn position
+			// jumps by however far the prediction had drifted. Render
+			// interpolation cannot hide that: it smooths within a step,
+			// and this is a discontinuity in the stepped values
+			// themselves. If the interval is a few per second and the
+			// correction is tens of centimetres, that is a tick a few
+			// times a second - which is the symptom being chased.
+			//
+			// Reported per entity, on a five second clock, so a busy race
+			// does not bury the log.
+			//
+			if (RPCameraLog() && GetInstance() == ReplicantInstance)
+			{
+				static Scalar next_say = 0.0f;
+				static int corrections = 0;
+				static Scalar worst = 0.0f;
+				static Scalar total = 0.0f;
+
+				Vector3D drift;
+				drift.Subtract(
+					update->localOrigin.linearPosition,
+					localOrigin.linearPosition
+				);
+				Scalar distance = drift.Length();
+				++corrections;
+				total += distance;
+				if (distance > worst)
+				{
+					worst = distance;
+				}
+
+				if ((Scalar) Now() >= next_say)
+				{
+					if (next_say > 0.0f && corrections > 0)
+					{
+						DEBUG_STREAM << "CamLog: replicant corrections - "
+							<< corrections << " in 5s ("
+							<< (corrections / 5) << "/s), mean "
+							<< (total / corrections) << "m, worst "
+							<< worst << "m\n" << std::flush;
+					}
+					next_say = ((Scalar) Now()) + 5.0f;
+					corrections = 0;
+					worst = 0.0f;
+					total = 0.0f;
+				}
+			}
+
 			updateOrigin = update->localOrigin;
 
 			//