diff --git a/rugnux/RugnuxFirstPassRescues.cpp b/rugnux/RugnuxFirstPassRescues.cpp
index e3baace32..0c7b4b0c7 100644
--- a/rugnux/RugnuxFirstPassRescues.cpp
+++ b/rugnux/RugnuxFirstPassRescues.cpp
@@ -855,7 +855,19 @@ auto Rugnux::FirstPassRun::CentresDisagree(FirstPass best, const FirstPass &alt,
             RestoreBeamCenter(header_x, header_y);
         }
     }
-    if (!adopted_measured)
+    // The pooled excess is a near tie on a harmonic pair more often than not: the larger cell's extra
+    // nodes catch the spots a wrong centre displaces, and its own null grows with them. Measured on a
+    // small-molecule crystal whose file centre sat 4 px out across the spindle: 12.8x over chance at
+    // the file's centre on the doubled cell against 13.9x at the measured one on the true cell, so the
+    // file's centre was kept and the run ended on a cell 1.6 % long. Rather than decide on that, carry
+    // the measured centre forward and judge the two arms on their merges (RunAllPasses), as the
+    // same-cell case above does.
+    if (!adopted_measured && integer_harmonic && geometry_prepass) {
+        rx.beam_center_alternative_ = std::array<float, 2>{measured_x, measured_y};
+        logger.Warning("Beam centre check: the pooled spots do not settle which of the two "
+                       "cells is the centre error, so the run keeps the file's centre for now "
+                       "and carries the measured one forward, adopting whichever merges better");
+    } else if (!adopted_measured)
         logger.Warning("Beam centre check: the run keeps the file's centre. The "
                        "frame counts cannot arbitrate this - a cell twice as long "
                        "must place every spot twice as accurately to score the "