diff --git a/MerlinAU.sh b/MerlinAU.sh
index 5ddaf63..e5bd398 100644
--- a/MerlinAU.sh
+++ b/MerlinAU.sh
@@ -4,13 +4,13 @@
 #
 # Original Creation Date: 2023-Oct-01 by @ExtremeFiretop.
 # Official Co-Author: @Martinski W. - Date: 2023-Nov-01
-# Last Modified: 2026-Mar-17
+# Last Modified: 2026-Mar-18
 ###################################################################
 set -u
 
 ## Set version for each Production Release ##
 readonly SCRIPT_VERSION=1.6.0
-readonly SCRIPT_VERSTAG="26031700"
+readonly SCRIPT_VERSTAG="26031823"
 readonly SCRIPT_NAME="MerlinAU"
 ## Set to "master" for Production Releases ##
 SCRIPT_BRANCH="dev"
@@ -409,7 +409,7 @@ readonly LockTypeRegEx="(cliMenuLock|cliOptsLock|cliFileLock)"
 _FindLockFileTypes_()
 { grep -woE "$LockTypeRegEx" "$LockFilePath" | tr '\n' ' ' | sed 's/[ ]*$//' ; }
 
-_ReleaseLock_() 
+_ReleaseLock_()
 {
    local lockType
    if [ $# -eq 0 ] || [ -z "$1" ]
@@ -421,7 +421,7 @@ _ReleaseLock_()
    then
        if [ -z "$lockType" ]
        then sed -i "/^$$|/d" "$LockFilePath"
-       else sed -i "/.*|${1}$/d" "$LockFilePath"
+       else sed -i "/^$$|${1}$/d" "$LockFilePath"
        fi
        [ -s "$LockFilePath" ] && return 0
    fi
@@ -476,8 +476,7 @@ _AcquireLock_()
    retCode=1
    lockTypeFound=""
    waitTimeoutSecs=0
-   savedVerbose="$isVerbose"
-   isVerbose=true
+   savedVerbose="$isVerbose" ; isVerbose=true
 
    while true
    do
@@ -531,6 +530,78 @@ _AcquireLock_()
    return "$retCode"
 }
 
+##-------------------------------------##
+## Added by Martinski W. [2026-Mar-18] ##
+##-------------------------------------##
+fwupMutexFLock_FD=576
+fwupMutexFLock_FN="/tmp/var/${ScriptFNameTag}_FW_Update.FLock"
+fwupMutexFLock_OK=false  #DO NOT have FLock#
+
+_ReleaseMutexFLock_()
+{
+    if [ $# -gt 0 ] && \
+       [ "$1" = "checkLockOK" ] && \
+       [ "$fwupMutexFLock_OK" != "true" ]
+    then return 0
+    fi
+
+    printf '' > "$fwupMutexFLock_FN"
+    flock -u "$fwupMutexFLock_FD" 2>/dev/null
+    fwupMutexFLock_OK=false
+}
+
+##-------------------------------------##
+## Added by Martinski W. [2026-Mar-18] ##
+##-------------------------------------##
+#--------------------------------------------------------------#
+# This is a mutually exclusive, non-blocking FLOCK mechanism
+# to be used when MerlinAU is perforning a F/W Update so that
+# AMTM can check and prevent running automatic script updates
+# while the F/W Update is in progress.
+#--------------------------------------------------------------#
+_AcquireMutexFLock_()
+{
+    local retCode  savedVerbose
+    local procInfo  procName  procIDno  procIDof=""
+
+    savedVerbose="$isVerbose" ; isVerbose=true
+
+    if [ -s "$fwupMutexFLock_FN" ]
+    then
+        procInfo="$(head -n1 "$fwupMutexFLock_FN")"
+        procName="$(echo "$procInfo" | cut -d'|' -f1)"
+        procIDno="$(echo "$procInfo" | cut -d'|' -f2)"
+        if [ -n "$procName" ] && [ -n "$procIDno" ]
+        then procIDof="$(pidof "$procName")"
+        fi
+        if [ -z "$procIDof" ] || \
+           ! echo "$procIDof" | grep -qow "$procIDno"
+        then
+            Say "Stale F/W Update Lock Found. Resetting lock file..."
+            _ReleaseMutexFLock_
+        fi
+    fi
+
+    [ ! -s "$fwupMutexFLock_FN" ] && \
+    eval exec "$fwupMutexFLock_FD>$fwupMutexFLock_FN"
+
+    if flock -x -n "$fwupMutexFLock_FD" 2>/dev/null
+    then
+        printf "$(basename "$0")|$$\n" > "$fwupMutexFLock_FN"
+        retCode=0 ; fwupMutexFLock_OK=true
+    else
+        procInfo="$(head -n1 "$fwupMutexFLock_FN")"
+        if [ -n "$procInfo" ]
+        then procInfo="$(echo "$procInfo" | sed 's/|/, PID=/')"
+        fi
+        Say "${REDct}**ERROR**${NOct}: Another process [$procInfo] has the F/W Update Lock file."
+        retCode=1 ; fwupMutexFLock_OK=false
+    fi
+
+    isVerbose="$savedVerbose"
+    return "$retCode"
+}
+
 ##-------------------------------------##
 ## Added by Martinski W. [2025-Sep-01] ##
 ##-------------------------------------##
@@ -544,7 +615,9 @@ _DoExit_()
 {
    local exitCode=0
    [ $# -gt 0 ] && [ -n "$1" ] && exitCode="$1"
-   _ReleaseLock_ ; exit "$exitCode"
+   _ReleaseLock_
+   _ReleaseMutexFLock_ checkLockOK
+   exit "$exitCode"
 }
 
 ##-------------------------------------##
@@ -9126,11 +9199,15 @@ _RunOfflineUpdateNow_()
                 FW_DL_FPATH="${FW_ZIP_DIR}/${FW_FileName}.${extension}"
                 _GnutonBuildSelection_
             fi
-            if _AcquireLock_ cliFileLock
+            if _AcquireLock_ cliFileLock && \
+               _AcquireMutexFLock_
             then
                 _RunFirmwareUpdateNow_
-                _ReleaseLock_ cliFileLock
+            else
+                _WaitForEnterKey_
             fi
+            _ReleaseLock_ cliFileLock
+            _ReleaseMutexFLock_ checkLockOK
             _ClearOfflineUpdateState_
         else
             _ClearOfflineUpdateState_ 1
@@ -9953,10 +10030,12 @@ _PostRebootRunNow_()
 
    Say "END of $logMsg [$curWaitDelaySecs sec.]"
    sleep 30  ## Let's wait a bit & proceed ##
-   if _AcquireLock_ cliFileLock
+   if _AcquireLock_ cliFileLock && \
+      _AcquireMutexFLock_
    then
        _RunFirmwareUpdateNow_
        _ReleaseLock_ cliFileLock
+       _ReleaseMutexFLock_
    fi
 }
 
@@ -11615,12 +11694,16 @@ _MainMenu_()
                  HIDE_ROUTER_SECTION=true
              fi
              ;;
-          1) if _AcquireLock_ cliFileLock
+          1) if _AcquireLock_ cliFileLock && \
+                _AcquireMutexFLock_
              then
                  _RunFirmwareUpdateNow_
-                 _ReleaseLock_ cliFileLock
                  FlashStarted=false
+             else
+                 _WaitForEnterKey_
              fi
+             _ReleaseLock_ cliFileLock
+             _ReleaseMutexFLock_ checkLockOK
              ;;
           2) _GetLoginCredentials_
              ;;
@@ -11822,10 +11905,12 @@ then
 
    case "$1" in
        run_now)
-           if _AcquireLock_ cliFileLock
+           if _AcquireLock_ cliFileLock && \
+              _AcquireMutexFLock_
            then
                _RunFirmwareUpdateNow_
                _ReleaseLock_ cliFileLock
+               _ReleaseMutexFLock_
            fi
            ;;
        processNodes) _ProcessMeshNodes_ false
@@ -11914,7 +11999,8 @@ then
                        ;;
                    "${SCRIPT_NAME}checkfwupdate" | \
                    "${SCRIPT_NAME}checkfwupdate_bypassDays")
-                       if _AcquireLock_ cliFileLock
+                       if _AcquireLock_ cliFileLock && \
+                          _AcquireMutexFLock_
                        then
                            if [ "$3" = "${SCRIPT_NAME}checkfwupdate_bypassDays" ]
                            then bypassPostponedDays=true
@@ -11923,6 +12009,7 @@ then
                            webguiMode=true
                            _RunFirmwareUpdateNow_
                            _ReleaseLock_ cliFileLock
+                           _ReleaseMutexFLock_
                        fi
                        ;;
                    "${SCRIPT_NAME}scrptupdate" | \
diff --git a/README.md b/README.md
index c1eb7be..6aa619f 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # MerlinAU - AsusWRT-Merlin Firmware Auto Updater
 
 ## v1.6.0
-## 2026-Mar-17
+## 2026-Mar-19
 
 ## WebUI:
 ![image](https://github.com/user-attachments/assets/9c1dff99-9c13-491b-a7fa-aff924d5f02e)