Index: firmware/App/Services/SystemComm.c
===================================================================
diff -u -r191dc55c1d5b75415f4c67b07df1b569a1454034 -r1da5fe992c0b461115912698afc9cc7039ad2df3
--- firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 191dc55c1d5b75415f4c67b07df1b569a1454034)
+++ firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 1da5fe992c0b461115912698afc9cc7039ad2df3)
@@ -7,8 +7,8 @@
 *
 * @file    SystemComm.c
 *
-* @author  (last)      Sean Nash
-* @date    (last)      24-Aug-2023
+* @author  (last)      Michael Garthwaite
+* @date    (last)      05-Sep-2023
 *
 * @author  (original)  Dara Navaei
 * @date    (original)  05-Nov-2019
@@ -56,6 +56,9 @@
 #define MAX_FPGA_CLOCK_SPEED_ERRORS             3                           ///< maximum number of FPGA clock speed errors within window period before alarm
 #define MAX_FPGA_CLOCK_SPEED_ERROR_WINDOW_MS    (10 * SEC_PER_MIN * MS_PER_SECOND)    ///< FPGA clock speed error window
 
+#define PENDING_ACK_LIST_OVERRIDE_UI_CHANNEL    1                                     ///< Value for determining UI channel when Pending ACKs are overriden.
+#define PENDING_ACK_LIST_OVERRIDE_DG_CHANNEL    2                                     ///< Value for determining HD channel when Pending ACKs are overriden.
+
 #pragma pack(push, 1)
 
 /// Record for transmitted message that is pending acknowledgement from receiver.
@@ -750,13 +753,18 @@
     BOOL result = FALSE;
     U32  i;
 
-    // find match
+    // Find match
     for ( i = 0; i < PENDING_ACK_LIST_SIZE; i++ )
     {
         if ( ( TRUE == pendingAckList[ i ].used ) && ( pendingAckList[ i ].seqNo == seqNo ) )
-        {   // remove message pending ACK from list
-            pendingAckList[ i ].used = FALSE;
+        {
             result = TRUE;
+            // Remove message pending ACK from list
+            if ( ( ( getU32OverrideValue( &pendingACKOverride ) != PENDING_ACK_LIST_OVERRIDE_UI_CHANNEL ) || ( pendingAckList[ i ].channel != COMM_BUFFER_OUT_CAN_DG_2_UI ) ) &&
+                 ( ( getU32OverrideValue( &pendingACKOverride ) != PENDING_ACK_LIST_OVERRIDE_DG_CHANNEL ) || ( pendingAckList[ i ].channel != COMM_BUFFER_OUT_CAN_DG_2_HD ) ) )
+            {
+                pendingAckList[ i ].used = FALSE;
+            }
             break;
         }
     }
@@ -782,7 +790,7 @@
     {
         for ( i = 0; i < PENDING_ACK_LIST_SIZE; i++ )
         {   // pending ACK expired?
-            if ( ( TRUE == pendingAckList[ i ].used ) && ( ( TRUE == didTimeout( pendingAckList[ i ].timeStamp, MSG_NOT_ACKED_TIMEOUT_MS ) ) ||  ( getU32OverrideValue( &pendingACKOverride ) > 0 ) ) )
+            if ( ( TRUE == pendingAckList[ i ].used ) && ( TRUE == didTimeout( pendingAckList[ i ].timeStamp, MSG_NOT_ACKED_TIMEOUT_MS ) ) )
             {   // if retries left, reset and resend pending message. Do not retry when in POST since the UI might not still be responsive
                 if ( pendingAckList[ i ].retries > 0 )
                 {