diff --git a/src/components/ProgressMonitor/ProgressMonitor.tsx b/src/components/ProgressMonitor/ProgressMonitor.tsx
index 2d26bad..1cf3d6e 100644
--- a/src/components/ProgressMonitor/ProgressMonitor.tsx
+++ b/src/components/ProgressMonitor/ProgressMonitor.tsx
@@ -71,12 +71,12 @@ export function ProgressMonitor() {
   const isMaskTraceComplete =
     machineStatus === MachineStatus.MASK_TRACE_COMPLETE;
 
-  // Use PEN stitch count as fallback when machine reports 0 total stitches
-  const totalStitches = patternInfo
-    ? patternInfo.totalStitches === 0 && displayPattern?.penStitches
-      ? displayPattern.penStitches.stitches.length
-      : patternInfo.totalStitches
-    : 0;
+  // Use our own PEN stitch count as the source of truth for total stitches.
+  // The machine's patternInfo.totalStitches uses a different counting method than
+  // currentStitch (e.g. excludes lock stitches), so it can't be used as the max.
+  const totalStitches = displayPattern?.penStitches
+    ? displayPattern.penStitches.stitches.length
+    : (patternInfo?.totalStitches ?? 0);
 
   // Use adjustedStitchIndex (from step control) when available, otherwise machine-reported
   const currentStitch =
@@ -156,8 +156,10 @@ export function ProgressMonitor() {
             totalStitches={totalStitches}
             lastRolledBackError={lastRolledBackError}
             colorBlocks={colorBlocks}
-            onAdjustPosition={adjustStitchPosition}
-            onSetPosition={setStitchPosition}
+            onAdjustPosition={(offset) =>
+              adjustStitchPosition(offset, totalStitches)
+            }
+            onSetPosition={(index) => setStitchPosition(index, totalStitches)}
           />
         )}
 
diff --git a/src/stores/useMachineStore.ts b/src/stores/useMachineStore.ts
index de9faa3..10ba897 100644
--- a/src/stores/useMachineStore.ts
+++ b/src/stores/useMachineStore.ts
@@ -65,8 +65,8 @@ interface MachineState {
   startSewing: () => Promise<void>;
   resumeSewing: () => Promise<void>;
   deletePattern: () => Promise<void>;
-  setStitchPosition: (index: number) => Promise<void>;
-  adjustStitchPosition: (offset: number) => Promise<void>;
+  setStitchPosition: (index: number, maxStitches?: number) => Promise<void>;
+  adjustStitchPosition: (offset: number, maxStitches?: number) => Promise<void>;
 
   // Initialization
   initialize: () => void;
@@ -338,11 +338,11 @@ export const useMachineStore = create<MachineState>((set, get) => ({
   },
 
   // Set stitch position to an absolute index
-  setStitchPosition: async (index: number) => {
+  setStitchPosition: async (index: number, maxStitches?: number) => {
     const { isConnected, service, patternInfo } = get();
     if (!isConnected) return;
 
-    const totalStitches = patternInfo?.totalStitches || 0;
+    const totalStitches = maxStitches ?? patternInfo?.totalStitches ?? 0;
     const clamped = Math.max(0, Math.min(index, totalStitches));
 
     try {
@@ -359,11 +359,11 @@ export const useMachineStore = create<MachineState>((set, get) => ({
   },
 
   // Adjust stitch position by a relative offset
-  adjustStitchPosition: async (offset: number) => {
+  adjustStitchPosition: async (offset: number, maxStitches?: number) => {
     const { sewingProgress, adjustedStitchIndex } = get();
     const currentIndex =
       adjustedStitchIndex ?? sewingProgress?.currentStitch ?? 0;
-    await get().setStitchPosition(currentIndex + offset);
+    await get().setStitchPosition(currentIndex + offset, maxStitches);
   },
 
   // Handle automatic stitch rollback for thread errors