diff --git a/beast/observationmodel/ast/make_ast_input_list.py b/beast/observationmodel/ast/make_ast_input_list.py
index b7f6bea1..ad1d5b74 100755
--- a/beast/observationmodel/ast/make_ast_input_list.py
+++ b/beast/observationmodel/ast/make_ast_input_list.py
@@ -185,7 +185,7 @@ def pick_models_toothpick_style(
             else:
                 # ... do not include this model again, since we will reject it
                 # anyway.
-                include_mask[idxs == rand_idx] = False
+                include_mask[idxs == rand_idx[r]] = False
 
         # Add the approved models
         chosen_idxs.extend(rand_idx[add_these])
diff --git a/beast/physicsmodel/grid_and_prior_weights.py b/beast/physicsmodel/grid_and_prior_weights.py
index 4978efe0..dd056daa 100644
--- a/beast/physicsmodel/grid_and_prior_weights.py
+++ b/beast/physicsmodel/grid_and_prior_weights.py
@@ -94,7 +94,7 @@ def compute_distance_age_mass_metallicity_weights(
         dist_prior_weights /= np.sum(dist_prior_weights)
         dist_weights = dist_grid_weights * dist_prior_weights
 
-        # correct for any non-unformity in the number size of the
+        # correct for any non-uniformity in the number size of the
         # age-mass grids between metallicity points
         total_dist_grid_weight /= np.sum(total_dist_grid_weight)
         total_dist_prior_weight /= np.sum(total_dist_prior_weight)
@@ -180,6 +180,10 @@ def compute_age_mass_metallicity_weights(
                     mass_prior = mass_prior_model
 
                 # deal with repeat masses - happens for MegaBEAST
+                # and have discovred this can happen even for a standard BEAST run
+                # as sometimes two masses in an isochrone are exactly the same
+                #   new code for MegaBEAST is more correct as then the grid weight
+                #   will be correctly set for any repeated masses
                 cur_masses = np.unique(_tgrid_single_age["M_ini"])
                 n_masses = len(_tgrid_single_age["M_ini"])
                 if len(cur_masses) < n_masses: