diff --git a/src/module/mifare.cpp b/src/module/mifare.cpp
index 7f7398e..0531a0c 100644
--- a/src/module/mifare.cpp
+++ b/src/module/mifare.cpp
@@ -691,10 +691,14 @@ void Mifare::writeSelected(TargetType targetType)
             {
                 result = _writeblk(item, KEY_B, keyBList->at(data_b2s(item)), dataList->at(item), TARGET_MIFARE);
             }
-            if(!result)
+            if(!result && keyAList->at(data_b2s(item)) != "FFFFFFFFFFFF")
             {
                 result = _writeblk(item, KEY_A, "FFFFFFFFFFFF", dataList->at(item), TARGET_MIFARE);
             }
+            if(!result && keyBList->at(data_b2s(item)) != "FFFFFFFFFFFF") // for access bits like "80 f7 87", the block can only be written with keyB
+            {
+                result = _writeblk(item, KEY_B, "FFFFFFFFFFFF", dataList->at(item), TARGET_MIFARE);
+            }
         }
         else // key doesn't matter when writing to Chinese Magic Card and Emulator Memory
         {
diff --git a/src/ui/mainwindow.cpp b/src/ui/mainwindow.cpp
index d2e338b..59efc1d 100644
--- a/src/ui/mainwindow.cpp
+++ b/src/ui/mainwindow.cpp
@@ -30,7 +30,9 @@ MainWindow::MainWindow(QWidget *parent):
     settings->setIniCodec("UTF-8");
 
     pm3Thread = new QThread(this);
+    connect(QApplication::instance(), &QApplication::aboutToQuit, pm3Thread, &QThread::quit);
     pm3 = new PM3Process(pm3Thread);
+    connect(pm3Thread, &QThread::finished, pm3, &PM3Process::deleteLater);
     pm3Thread->start();
     pm3state = false;
     clientWorkingDir = new QDir;