diff --git a/src/classes/PMusrCanvas.cpp b/src/classes/PMusrCanvas.cpp
index 0d7ee761..cffd4f0a 100644
--- a/src/classes/PMusrCanvas.cpp
+++ b/src/classes/PMusrCanvas.cpp
@@ -95,7 +95,7 @@ PMusrCanvas::PMusrCanvas(const int number, const char* title,
  */
 PMusrCanvas::~PMusrCanvas()
 {
-cout << "~PMusrCanvas() called" << endl;
+cout << "~PMusrCanvas() called. fMainCanvas name=" << fMainCanvas->GetName() << endl;
   // cleanup
   if (fStyle) {
     delete fStyle;
@@ -332,7 +332,7 @@ void PMusrCanvas::UpdateParamTheoryPad()
     if (param[i].fPosErrorPresent) { // minos was used
       // calculate the arithmetic average of the pos. and neg. error
       double err;
-      err = param[i].fPosError + param[i].fStep / 2.0;
+      err = (param[i].fPosError - param[i].fStep) / 2.0;
       // check if the pos. and neg. error within 10%
       if ((fabs(fabs(param[i].fStep) - param[i].fPosError) < 0.1*fabs(param[i].fStep)) &&
           (fabs(fabs(param[i].fStep) - param[i].fPosError) < 0.1*param[i].fPosError)) {
diff --git a/src/musrview.cpp b/src/musrview.cpp
index 8cf90b75..995a1ac4 100644
--- a/src/musrview.cpp
+++ b/src/musrview.cpp
@@ -38,6 +38,7 @@ using namespace std;
 
 #include <TApplication.h>
 #include <TSAXParser.h>
+#include <TROOT.h>
 
 #include "PMusr.h"
 #include "PStartupHandler.h"
@@ -264,9 +265,16 @@ cout << endl;
 
     // clean up
 cout << endl << "clean up canvas vector ...";
+    char canvasName[32];
     for (unsigned int i=0; i<canvasVector.size(); i++) {
       // check if canvas is still there before calling the destructor **TO BE DONE**
-      canvasVector[i]->~PMusrCanvas();
+      sprintf(canvasName, "fMainCanvas%d", i);
+cout << endl << ">> canvasName=" << canvasName;
+      if (gROOT->GetListOfCanvases()->FindObject(canvasName) != 0) {
+cout << endl << ">> canvasName=" << canvasName << ", found ...";
+cout << endl;
+        canvasVector[i]->~PMusrCanvas();
+      }
     }
     canvasVector.empty();
   }