diff --git a/routes/sstv_general.py b/routes/sstv_general.py
index 0ddcbfb..63d4f8d 100644
--- a/routes/sstv_general.py
+++ b/routes/sstv_general.py
@@ -13,6 +13,7 @@ from pathlib import Path
 
 from flask import Blueprint, Response, jsonify, request, send_file
 
+import app as app_module
 from utils.logging import get_logger
 from utils.sse import format_sse
 from utils.event_pipeline import process_event
@@ -27,6 +28,9 @@ sstv_general_bp = Blueprint('sstv_general', __name__, url_prefix='/sstv-general'
 # Queue for SSE progress streaming
 _sstv_general_queue: queue.Queue = queue.Queue(maxsize=100)
 
+# Track which device is being used
+_sstv_general_active_device: int | None = None
+
 # Predefined SSTV frequencies
 SSTV_FREQUENCIES = [
     {'band': '80 m', 'frequency': 3.845, 'modulation': 'lsb', 'notes': 'Common US SSTV calling frequency', 'type': 'Terrestrial HF'},
@@ -150,6 +154,17 @@ def start_decoder():
             'message': 'Modulation must be fm, usb, or lsb',
         }), 400
 
+    # Claim SDR device
+    global _sstv_general_active_device
+    device_int = int(device_index)
+    error = app_module.claim_sdr_device(device_int, 'sstv_general')
+    if error:
+        return jsonify({
+            'status': 'error',
+            'error_type': 'DEVICE_BUSY',
+            'message': error,
+        }), 409
+
     # Set callback and start
     decoder.set_callback(_progress_callback)
     success = decoder.start(
@@ -159,6 +174,7 @@ def start_decoder():
     )
 
     if success:
+        _sstv_general_active_device = device_int
         return jsonify({
             'status': 'started',
             'frequency': frequency,
@@ -166,6 +182,7 @@ def start_decoder():
             'device': device_index,
         })
     else:
+        app_module.release_sdr_device(device_int)
         return jsonify({
             'status': 'error',
             'message': 'Failed to start decoder',
@@ -175,8 +192,14 @@ def start_decoder():
 @sstv_general_bp.route('/stop', methods=['POST'])
 def stop_decoder():
     """Stop general SSTV decoder."""
+    global _sstv_general_active_device
     decoder = get_general_sstv_decoder()
     decoder.stop()
+
+    if _sstv_general_active_device is not None:
+        app_module.release_sdr_device(_sstv_general_active_device)
+        _sstv_general_active_device = None
+
     return jsonify({'status': 'stopped'})
 
 
diff --git a/utils/sstv/sstv_decoder.py b/utils/sstv/sstv_decoder.py
index 498d52e..20f3eba 100644
--- a/utils/sstv/sstv_decoder.py
+++ b/utils/sstv/sstv_decoder.py
@@ -475,6 +475,7 @@ class SSTVDecoder:
                         mode_spec = get_mode(vis_code)
                         if mode_spec:
                             current_mode_name = mode_name
+                            last_partial_pct = -1
                             image_decoder = SSTVImageDecoder(
                                 mode_spec,
                                 sample_rate=SAMPLE_RATE,
diff --git a/utils/sstv/vis.py b/utils/sstv/vis.py
index 1f014e4..50a83c2 100644
--- a/utils/sstv/vis.py
+++ b/utils/sstv/vis.py
@@ -298,16 +298,26 @@ class VISDetector:
 
             if self._tone_counter >= self._bit_windows:
                 result = self._validate_and_decode()
-                # Do NOT call reset() here. self._buffer still holds samples
-                # that arrived after the STOP_BIT window — those are the very
-                # first samples of the image. Wiping the buffer here causes all
-                # of them to be lost, making the image decoder start mid-stream
-                # and producing garbled/diagonal output.
-                # feed() will advance past the current window, leaving
-                # self._buffer pointing at the image start. The caller must
-                # read remaining_buffer and then call reset() explicitly.
-                self._state = VISState.DETECTED
-                return result
+                if result is not None:
+                    # Do NOT call reset() here. self._buffer still holds
+                    # samples that arrived after the STOP_BIT window — those
+                    # are the very first samples of the image. Wiping the
+                    # buffer here causes all of them to be lost, making the
+                    # image decoder start mid-stream and producing
+                    # garbled/diagonal output.
+                    # feed() will advance past the current window, leaving
+                    # self._buffer pointing at the image start. The caller
+                    # must read remaining_buffer and then call reset().
+                    self._state = VISState.DETECTED
+                    return result
+                else:
+                    # Parity failure or unknown VIS code — reset and
+                    # continue scanning for the next VIS header.
+                    self._tone_counter = 0
+                    self._data_bits = []
+                    self._parity_bit = 0
+                    self._bit_accumulator = []
+                    self._state = VISState.IDLE
 
         elif self._state == VISState.DETECTED:
             # Waiting for caller to call reset() after reading remaining_buffer.