diff --git a/.github/workflows/Build.yml b/.github/workflows/Build.yml
index cb6874a7..9b09f14e 100644
--- a/.github/workflows/Build.yml
+++ b/.github/workflows/Build.yml
@@ -12,7 +12,7 @@ jobs:
   PC_Application_Ubuntu:
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |
@@ -44,7 +44,7 @@ jobs:
       - name: Upload artifact
         env: 
           LIBREVNA_VERSION: "${{steps.id_version.outputs.app_version}}"
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: LibreVNA-GUI-Ubuntu-${{env.LIBREVNA_VERSION}}
           path: Software/PC_Application/LibreVNA-GUI/LibreVNA-GUI
@@ -52,7 +52,7 @@ jobs:
   PC_Application_RPi5:
     runs-on: RPi-HIL
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |
@@ -82,7 +82,7 @@ jobs:
       - name: Upload artifact
         env: 
           LIBREVNA_VERSION: "${{steps.id_version.outputs.app_version}}"
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: LibreVNA-GUI-RPi5-${{env.LIBREVNA_VERSION}}
           path: Software/PC_Application/LibreVNA-GUI/LibreVNA-GUI          
@@ -90,7 +90,7 @@ jobs:
   PC_Application_Windows:
     runs-on: windows-2019
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
       - uses: msys2/setup-msys2@v2
 
       - name: Install Qt
@@ -141,7 +141,7 @@ jobs:
         shell: cmd
         
       - name: Upload
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         env: 
           LIBREVNA_VERSION: "${{steps.id_version.outputs.app_version}}"
         with:
@@ -149,13 +149,13 @@ jobs:
           path: Software/PC_Application/LibreVNA-GUI/release
 
   PC_Application_OSX:
-    runs-on: macos-12
+    runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |
-          brew install qt@6 libusb pcre
+          brew install qt@6 pcre
           
       - name: Set Environment
         run: |
@@ -189,7 +189,7 @@ jobs:
       - name: Upload artifact
         env: 
           LIBREVNA_VERSION: "${{steps.id_version.outputs.app_version}}"
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: LibreVNA-GUI-OSX-${{env.LIBREVNA_VERSION}}
           path: Software/PC_Application/LibreVNA-GUI/LibreVNA-GUI.zip
@@ -197,7 +197,7 @@ jobs:
   Embedded_Firmware:
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Install toolchain
         run: |
@@ -230,7 +230,7 @@ jobs:
         shell: bash
 
       - name: Upload
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         env: 
           LIBREVNA_VERSION: "${{steps.id_version.outputs.app_version}}"
         with:
diff --git a/.github/workflows/Release_tag_stable.yml b/.github/workflows/Release_tag_stable.yml
index 8657d9c2..3e3f12b9 100644
--- a/.github/workflows/Release_tag_stable.yml
+++ b/.github/workflows/Release_tag_stable.yml
@@ -12,7 +12,7 @@ jobs:
     outputs:
       upload_url: ${{ steps.bump_release.outputs.upload_url }} 
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |
@@ -67,7 +67,7 @@ jobs:
     needs: PC_Application_Ubuntu
     runs-on: RPi-HIL
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |
@@ -106,7 +106,7 @@ jobs:
     needs: PC_Application_Ubuntu
     runs-on: windows-2019
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
       - uses: msys2/setup-msys2@v2
 
       - name: Install Qt
@@ -171,13 +171,13 @@ jobs:
           
   PC_Application_OSX:
     needs: PC_Application_Ubuntu
-    runs-on: macos-12
+    runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |
-          brew install qt@6 libusb pcre
+          brew install qt@6 pcre
           
       - name: Set Environment
         run: |
@@ -219,7 +219,7 @@ jobs:
     needs: PC_Application_Ubuntu
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Install toolchain
         run: |
diff --git a/Software/PC_Application/LibreVNA-GUI/Calibration/LibreCAL/caldevice.cpp b/Software/PC_Application/LibreVNA-GUI/Calibration/LibreCAL/caldevice.cpp
index 24bed2ab..9a827f37 100644
--- a/Software/PC_Application/LibreVNA-GUI/Calibration/LibreCAL/caldevice.cpp
+++ b/Software/PC_Application/LibreVNA-GUI/Calibration/LibreCAL/caldevice.cpp
@@ -243,7 +243,7 @@ void CalDevice::loadCoefficientSetsThreadSlow(QStringList names, QList<int> port
             totalPoints += usb->Query(":COEFF:NUM? "+name+" P"+QString::number(i)+"_SHORT").toInt();
             totalPoints += usb->Query(":COEFF:NUM? "+name+" P"+QString::number(i)+"_LOAD").toInt();
             for(int jdx=idx+1;jdx<numPorts;jdx++) {
-                int j = ports[j];
+                int j = ports[jdx];
                 totalPoints += usb->Query(":COEFF:NUM? "+name+" P"+QString::number(i)+QString::number(j)+"_THROUGH").toInt();
             }
         }
diff --git a/Software/PC_Application/LibreVNA-GUI/Device/LibreVNA/Compound/compounddeviceeditdialog.cpp b/Software/PC_Application/LibreVNA-GUI/Device/LibreVNA/Compound/compounddeviceeditdialog.cpp
index 0fc74ff2..331a0056 100644
--- a/Software/PC_Application/LibreVNA-GUI/Device/LibreVNA/Compound/compounddeviceeditdialog.cpp
+++ b/Software/PC_Application/LibreVNA-GUI/Device/LibreVNA/Compound/compounddeviceeditdialog.cpp
@@ -126,7 +126,7 @@ void CompoundDeviceEditDialog::checkIfOkay()
     // Check port mapping
     // Looking for duplicate and missing ports
     bool highestPortFound = false;
-    unsigned int highestPort;
+    unsigned int highestPort = 0;
     for(unsigned int port=0;port<2*ldev.deviceSerials.size();port++) {
         int num = 0;
         for(unsigned int i=0;i<deviceFrames.size();i++) {
diff --git a/Software/PC_Application/LibreVNA-GUI/VNA/vna.cpp b/Software/PC_Application/LibreVNA-GUI/VNA/vna.cpp
index cf39e2b4..c6575b3c 100644
--- a/Software/PC_Application/LibreVNA-GUI/VNA/vna.cpp
+++ b/Software/PC_Application/LibreVNA-GUI/VNA/vna.cpp
@@ -646,7 +646,7 @@ VNA::VNA(AppWindow *window, QString name)
 
 Calibration::InterpolationType VNA::getCalInterpolation()
 {
-    double f_min, f_max;
+    double f_min = 0, f_max = 0;
     switch(settings.sweepType) {
     case SweepType::Last:
         // should never get here, use frequency values just in case
@@ -976,7 +976,7 @@ void VNA::NewDatapoint(DeviceDriver::VNAMeasurement m)
         window->addStreamingData(m_avg, AppWindow::VNADataType::Calibrated);
     }
 
-    TraceMath::DataType type;
+    TraceMath::DataType type = TraceMath::DataType::Frequency;
     if(settings.zerospan) {
         type = TraceMath::DataType::TimeZeroSpan;