diff --git a/image_analysis/scale_merge/AnisotropyAnalysis.cpp b/image_analysis/scale_merge/AnisotropyAnalysis.cpp
index f3aef175..893389bf 100644
--- a/image_analysis/scale_merge/AnisotropyAnalysis.cpp
+++ b/image_analysis/scale_merge/AnisotropyAnalysis.cpp
@@ -612,6 +612,10 @@ namespace {
 
     // ---------------------------------------------------------------- the s^2 signature
     struct ShapeFit {
+        // The regressions below all ran. Distinct from shells: there can be plenty of shells and
+        // still no fit, and a ShapeFit that returned early carries NaN coefficients with flat and
+        // convex both false - which reads as a clean "Linear" to anyone testing those two alone.
+        bool ok = false;
         int shells = 0;
         double c0 = NAN, c0_err = NAN, c1 = NAN, slope_through_origin = NAN;
         double curvature = NAN, curvature_err = NAN, curvature_share = NAN;
@@ -771,6 +775,7 @@ namespace {
         out.convex = !out.flat && out.curvature > 0.0 && out.curvature_err > 0.0
                      && out.curvature / out.curvature_err > SHAPE_Z
                      && out.curvature_share > CONVEX_SHARE;
+        out.ok = true;
         return out;
     }
 
@@ -1236,14 +1241,17 @@ AnisotropyResult AnalyzeAnisotropy(const std::vector<MergedReflection> &merged,
 
     // --- the resolution signature, and whether the binning decides it ---
     const ShapeFit shape = FitShape(cells, constrained.b);
-    result.shape_shells = shape.shells;
+    // A fit that did not run was fitted over no shells. Reported that way rather than as the shells
+    // it had available, so the renderer and the cautions below do not print NaN coefficients beside a
+    // shell count that suggests they mean something.
+    result.shape_shells = shape.ok ? shape.shells : 0;
     result.shape_intercept = shape.c0;
     result.shape_intercept_z = shape.c0_err > 0.0 ? shape.c0 / shape.c0_err : NAN;
     result.shape_slope = shape.c1;
     result.shape_curvature_z = shape.curvature_err > 0.0 ? shape.curvature / shape.curvature_err : NAN;
     result.shape_curvature_share = shape.curvature_share;
     result.shape_residual = shape.residual;
-    if (shape.shells >= MIN_SHAPE_SHELLS) {
+    if (shape.ok && shape.shells >= MIN_SHAPE_SHELLS) {
         result.shape = shape.flat ? AnisotropyShape::Flat
                      : shape.convex ? AnisotropyShape::Convex : AnisotropyShape::Linear;
         if (std::isfinite(shape.slope_through_origin) && shape.slope_through_origin != 0.0) {
@@ -1262,7 +1270,7 @@ AnisotropyResult AnalyzeAnisotropy(const std::vector<MergedReflection> &merged,
                 break;
             }
             const ShapeFit alt_shape = FitShape(alt_cells, alt_fit.b);
-            if (alt_shape.shells < MIN_SHAPE_SHELLS || alt_shape.flat != shape.flat) {
+            if (!alt_shape.ok || alt_shape.shells < MIN_SHAPE_SHELLS || alt_shape.flat != shape.flat) {
                 result.shape_stable = false;
                 break;
             }
@@ -1341,7 +1349,7 @@ AnisotropyResult AnalyzeAnisotropy(const std::vector<MergedReflection> &merged,
         result.cautions.emplace_back(
                 "the directional deficit does not follow exp(-1/2 s^T B s), so the fitted deltaB is a fit "
                 "of the wrong functional form and may be an under-estimate");
-    if (result.shape == AnisotropyShape::Undetermined && shape.shells >= MIN_SHAPE_SHELLS)
+    if (result.shape == AnisotropyShape::Undetermined && result.shape_shells >= MIN_SHAPE_SHELLS)
         result.cautions.emplace_back(
                 "the resolution signature changed when the shells were rebinned, so it is reported as "
                 "undetermined rather than as a measurement");
@@ -1391,7 +1399,11 @@ std::string AnisotropyToText(const AnisotropyResult &result) {
     os << "\n";
     if (std::isfinite(result.fold_weakening))
         os << "  Strongest / weakest direction at the resolution limit: " << result.fold_weakening << "x\n";
-    if (std::isfinite(result.d_min_axis[0]) || std::isfinite(result.d_min_axis[2])) {
+    // Every axis, not just the outer two: ConeLimits fills each independently, so a crystal whose
+    // first and third directions fall in cones too sparse to measure - but whose second is well
+    // covered - would otherwise suppress the whole line, d_min_spread included.
+    if (std::isfinite(result.d_min_axis[0]) || std::isfinite(result.d_min_axis[1])
+        || std::isfinite(result.d_min_axis[2])) {
         bool any_censored = false;
         os << "  d_min along the principal directions (<I/sigma(I)> = " << CONE_I_OVER_SIGMA
            << " in a " << CONE_HALF_ANGLE_DEG << " deg cone):";