Try deleting by tab id not model id.

src/sas/qtgui/MainWindow/DataExplorer.py

@@ -2065,7 +2065,7 @@ def updateTheoryFromPerspective(self, model_item):
         self.theory_model.appendRow(model_item)
         return model_item
 
-    def deleteIntermediateTheoryPlotsByModelID(self, model_id):
+    def deleteIntermediateTheoryPlotsByModelID(self, tab_id):
         """Given a model's ID, deletes all items in the theory item model which reference the same ID. Useful in the
         case of intermediate results disappearing when changing calculations (in which case you don't want them to be
         retained in the list)."""
@@ -2077,8 +2077,8 @@ def deleteIntermediateTheoryPlotsByModelID(self, model_id):
                 return
             match = GuiUtils.theory_plot_ID_pattern.match(data.id)
             if match:
-                item_model_id = match.groups()[-1]
-                if item_model_id == model_id:
+                item_tab_id = match.groups()[0]
+                if item_tab_id == tab_id:
                     # Only delete those identified as an intermediate plot
                     if match.groups()[2] not in (None, ""):
                         items_to_delete.append(item)

src/sas/qtgui/Perspectives/Fitting/FittingWidget.py

@@ -3287,7 +3287,7 @@ def complete1D(self, return_data):
         else:
             # delete theory items for the model, in order to get rid of any
             # redundant items, e.g. beta(Q), S_eff(Q)
-            self.communicate.deleteIntermediateTheoryPlotsSignal.emit(self.kernel_module.id)
+            self.communicate.deleteIntermediateTheoryPlotsSignal.emit(self.tab_id)
 
         self._appendPlotsPolyDisp(new_plots, return_data, fitted_data)