diff --git a/src/musredit_qt5/musredit/PFitOutputHandler.cpp b/src/musredit_qt5/musredit/PFitOutputHandler.cpp
index 527845d7..7d1da209 100644
--- a/src/musredit_qt5/musredit/PFitOutputHandler.cpp
+++ b/src/musredit_qt5/musredit/PFitOutputHandler.cpp
@@ -173,25 +173,49 @@ void PFitOutputHandler::processDone(int exitCode, QProcess::ExitStatus exitStatu
     qDebug() << "**ERROR** PFitOutputHandler::processDone: exitCode = " << exitCode << Qt::endl;
 #endif
   }
-  fQuitButton->setText("Done");
+
+  if (fQuitRequested) {
+    // the process has now actually terminated in response to quitButtonPressed(); close the dialog
+    accept();
+  } else {
+    fQuitButton->setText("Done");
+  }
 }
 
 //----------------------------------------------------------------------------------------------------
 /**
- * <p>If the quit button is pressed while the fit is still running, try to terminate musrfit, if this
- * does not work, try to kill musrfit.
+ * <p>If the quit button is pressed while the fit is still running, request musrfit to terminate
+ * (SIGTERM) and disable the button; a single-shot timer escalates to kill() (SIGKILL) if musrfit
+ * has not reacted within a few seconds. The dialog is NOT closed here: processDone() (connected to
+ * QProcess::finished()) calls accept() once the process has actually terminated.
+ *
+ * <p>This deliberately never blocks on QProcess::waitForFinished(). A blocking wait here would
+ * freeze the whole (modal) dialog for up to its default 30 s timeout with no user feedback, which
+ * in practice led users to force-quit musredit itself while musrfit was still being terminated -
+ * orphaning the musrfit process, since ~PFitOutputHandler() (the actual terminate/kill/kill-9
+ * safety net) never got the chance to run.
  */
 void PFitOutputHandler::quitButtonPressed()
 {
-  // if the fitting is still taking place, kill it
-  if (fProc->state() == QProcess::Running) {
-    fProc->terminate();
-    if (!fProc->waitForFinished()) {
-      fProc->kill();
-    }
+  if (fProc->state() == QProcess::NotRunning) {
+    accept();
+    return;
   }
 
-  accept();
+  if (fQuitRequested) // termination already in progress, ignore repeated clicks
+    return;
+  fQuitRequested = true;
+
+  fQuitButton->setEnabled(false);
+  fQuitButton->setText(tr("Terminating..."));
+  fProc->terminate();
+
+  // escalate to SIGKILL if musrfit does not react to SIGTERM in time
+  // (e.g. blocked in slow disk/NFS I/O); accept() happens via processDone()
+  QTimer::singleShot(5000, this, [this]() {
+    if (fProc->state() != QProcess::NotRunning)
+      fProc->kill();
+  });
 }
 
 //----------------------------------------------------------------------------------------------------
diff --git a/src/musredit_qt5/musredit/PFitOutputHandler.h b/src/musredit_qt5/musredit/PFitOutputHandler.h
index 90108382..89235920 100644
--- a/src/musredit_qt5/musredit/PFitOutputHandler.h
+++ b/src/musredit_qt5/musredit/PFitOutputHandler.h
@@ -65,6 +65,7 @@ class PFitOutputHandler : public QDialog
 private:
     Q_PID fProcPID;  ///< keeps the process PID
     std::unique_ptr<QProcess> fProc; ///< pointer to the musrfit process
+    bool fQuitRequested = false; ///< set once the user pressed Quit while the process was still running
 
     std::unique_ptr<QVBoxLayout> fVbox; ///< pointer to the dialog layout manager
     std::unique_ptr<QPlainTextEdit> fOutput; ///< the captured musrfit output is written (read only) into this text edit object.
diff --git a/src/musredit_qt6/musredit/PFitOutputHandler.cpp b/src/musredit_qt6/musredit/PFitOutputHandler.cpp
index 8e100255..92c7c938 100644
--- a/src/musredit_qt6/musredit/PFitOutputHandler.cpp
+++ b/src/musredit_qt6/musredit/PFitOutputHandler.cpp
@@ -217,7 +217,13 @@ void PFitOutputHandler::processDone(int exitCode, QProcess::ExitStatus exitStatu
   if ((exitStatus == QProcess::CrashExit) && (exitCode != 0)) {
     qDebug() << "**ERROR** PFitOutputHandler::processDone: exitCode = " << exitCode << Qt::endl;
   }
-  fQuitButton->setText("Done");
+
+  if (fQuitRequested) {
+    // the process has now actually terminated in response to quitButtonPressed(); close the dialog
+    accept();
+  } else {
+    fQuitButton->setText("Done");
+  }
 }
 
 //----------------------------------------------------------------------------------------------------
@@ -226,25 +232,41 @@ void PFitOutputHandler::processDone(int exitCode, QProcess::ExitStatus exitStatu
  *
  * @details Handles user request to close the dialog. The behavior depends on
  * whether the fit is still running:
- * - If running: Attempts to terminate musrfit gracefully using QProcess::terminate().
- *   If graceful termination fails within the timeout period, forcefully kills
- *   the process using QProcess::kill().
- * - If finished: Simply closes the dialog.
+ * - If running: Requests graceful termination via QProcess::terminate() (SIGTERM)
+ *   and disables the button. A single-shot timer escalates to QProcess::kill()
+ *   (SIGKILL) if musrfit has not reacted within a few seconds. The dialog is
+ *   NOT closed here; processDone() (connected to QProcess::finished()) calls
+ *   accept() once the process has actually terminated.
+ * - If already finished: Simply closes the dialog.
  *
- * After ensuring the process is stopped (or was already stopped), accepts the
- * dialog (closes it with QDialog::Accepted result).
+ * @note This slot deliberately never blocks on QProcess::waitForFinished().
+ * A blocking wait here would freeze the whole (modal) dialog for up to its
+ * default 30 s timeout with no user feedback, which in practice led users to
+ * force-quit musredit itself while musrfit was still being terminated -
+ * orphaning the musrfit process, since ~PFitOutputHandler() (the actual
+ * terminate/kill/kill-9 safety net) never got the chance to run.
  */
 void PFitOutputHandler::quitButtonPressed()
 {
-  // if the fitting is still taking place, kill it
-  if (fProc->state() == QProcess::Running) {
-    fProc->terminate();
-    if (!fProc->waitForFinished()) {
-      fProc->kill();
-    }
+  if (fProc->state() == QProcess::NotRunning) {
+    accept();
+    return;
   }
 
-  accept();
+  if (fQuitRequested) // termination already in progress, ignore repeated clicks
+    return;
+  fQuitRequested = true;
+
+  fQuitButton->setEnabled(false);
+  fQuitButton->setText(tr("Terminating..."));
+  fProc->terminate();
+
+  // escalate to SIGKILL if musrfit does not react to SIGTERM in time
+  // (e.g. blocked in slow disk/NFS I/O); accept() happens via processDone()
+  QTimer::singleShot(5000, this, [this]() {
+    if (fProc->state() != QProcess::NotRunning)
+      fProc->kill();
+  });
 }
 
 //----------------------------------------------------------------------------------------------------
diff --git a/src/musredit_qt6/musredit/PFitOutputHandler.h b/src/musredit_qt6/musredit/PFitOutputHandler.h
index a7a5a605..2bac163c 100644
--- a/src/musredit_qt6/musredit/PFitOutputHandler.h
+++ b/src/musredit_qt6/musredit/PFitOutputHandler.h
@@ -132,6 +132,7 @@ class PFitOutputHandler : public QDialog
      */
     qint64 fProcPID;                   ///< Process ID of the running musrfit process.
     std::unique_ptr<QProcess> fProc;   ///< QProcess object managing the musrfit execution.
+    bool fQuitRequested = false;       ///< Set once the user pressed Quit while the process was still running.
     /** @} */
 
     /** @name UI Components