diff --git a/src/main.cpp b/src/main.cpp
index bb9bd64..b3cc989 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -27,6 +27,7 @@ static SenderStatus g_sender_statuses[NUM_SENDERS];
 static bool g_ap_mode = false;
 static WifiMqttConfig g_cfg;
 static uint32_t g_boot_ms = 0;
+static bool g_debug_forced_reboot_done = false;
 static FaultCounters g_sender_faults = {};
 static FaultCounters g_receiver_faults = {};
 static FaultCounters g_receiver_faults_published = {};
@@ -105,8 +106,17 @@ static uint32_t g_last_sync_request_ms = 0;
 static uint32_t g_build_attempts = 0;
 static uint32_t g_build_valid = 0;
 static uint32_t g_build_invalid = 0;
+static constexpr uint32_t DEBUG_FORCED_REBOOT_INTERVAL_MS = 3UL * 60UL * 60UL * 1000UL;
+
+enum class TxBuildError : uint8_t {
+  None = 0,
+  Encode = 1
+};
+
+static TxBuildError g_last_tx_build_error = TxBuildError::None;
 
 static void watchdog_kick();
+static void finish_inflight_batch();
 
 static void serial_debug_printf(const char *fmt, ...) {
   if (!SERIAL_DEBUG_MODE) {
@@ -391,6 +401,23 @@ static bool float_to_i16_w(float value, int16_t &out) {
   return true;
 }
 
+static int16_t float_to_i16_w_clamped(float value, bool &clamped) {
+  clamped = false;
+  if (isnan(value)) {
+    return 0;
+  }
+  long rounded = lroundf(value);
+  if (rounded < INT16_MIN) {
+    clamped = true;
+    return INT16_MIN;
+  }
+  if (rounded > INT16_MAX) {
+    clamped = true;
+    return INT16_MAX;
+  }
+  return static_cast<int16_t>(rounded);
+}
+
 static uint16_t battery_mv_from_voltage(float value) {
   if (isnan(value) || value <= 0.0f) {
     return 0;
@@ -536,6 +563,7 @@ static bool prepare_inflight_from_queue() {
 }
 
 static bool send_inflight_batch(uint32_t ts_for_display) {
+  g_last_tx_build_error = TxBuildError::None;
   if (!g_inflight_active) {
     return false;
   }
@@ -554,19 +582,44 @@ static bool send_inflight_batch(uint32_t ts_for_display) {
   input.err_tx = g_sender_faults.lora_tx_fail > 255 ? 255 : static_cast<uint8_t>(g_sender_faults.lora_tx_fail);
   input.err_last = static_cast<uint8_t>(g_sender_last_error);
   input.err_rx_reject = static_cast<uint8_t>(g_sender_rx_reject_reason);
+  uint8_t energy_regressions = 0;
+  uint8_t phase_clamps = 0;
   for (uint8_t i = 0; i < input.n; ++i) {
     input.energy_wh[i] = kwh_to_wh_from_float(g_inflight_samples[i].energy_total_kwh);
-    if (!float_to_i16_w(g_inflight_samples[i].phase_power_w[0], input.p1_w[i]) ||
-        !float_to_i16_w(g_inflight_samples[i].phase_power_w[1], input.p2_w[i]) ||
-        !float_to_i16_w(g_inflight_samples[i].phase_power_w[2], input.p3_w[i])) {
-      return false;
+    if (i > 0 && input.energy_wh[i] < input.energy_wh[i - 1]) {
+      input.energy_wh[i] = input.energy_wh[i - 1];
+      if (energy_regressions < 255) {
+        energy_regressions++;
+      }
     }
+    bool c1 = false;
+    bool c2 = false;
+    bool c3 = false;
+    input.p1_w[i] = float_to_i16_w_clamped(g_inflight_samples[i].phase_power_w[0], c1);
+    input.p2_w[i] = float_to_i16_w_clamped(g_inflight_samples[i].phase_power_w[1], c2);
+    input.p3_w[i] = float_to_i16_w_clamped(g_inflight_samples[i].phase_power_w[2], c3);
+    if (c1 && phase_clamps < 255) {
+      phase_clamps++;
+    }
+    if (c2 && phase_clamps < 255) {
+      phase_clamps++;
+    }
+    if (c3 && phase_clamps < 255) {
+      phase_clamps++;
+    }
+  }
+  if (SERIAL_DEBUG_MODE && (energy_regressions > 0 || phase_clamps > 0)) {
+    serial_debug_printf("tx: sanitize batch_id=%u energy_regress=%u phase_clamps=%u",
+                        g_inflight_batch_id,
+                        static_cast<unsigned>(energy_regressions),
+                        static_cast<unsigned>(phase_clamps));
   }
 
   static uint8_t encoded[BATCH_MAX_COMPRESSED];
   size_t encoded_len = 0;
   uint32_t encode_start = millis();
   if (!encode_batch(input, encoded, sizeof(encoded), &encoded_len)) {
+    g_last_tx_build_error = TxBuildError::Encode;
     return false;
   }
   uint32_t encode_ms = millis() - encode_start;
@@ -612,6 +665,13 @@ static bool send_meter_batch(uint32_t ts_for_display) {
     g_last_sent_batch_id = g_inflight_batch_id;
     g_batch_ack_pending = true;
   } else {
+    if (g_last_tx_build_error == TxBuildError::Encode) {
+      serial_debug_printf("tx: encode failed batch_id=%u dropped", g_inflight_batch_id);
+      note_fault(g_sender_faults, g_sender_last_error, g_sender_last_error_utc, g_sender_last_error_ms, FaultType::Decode);
+      display_set_last_error(g_sender_last_error, g_sender_last_error_utc, g_sender_last_error_ms);
+      finish_inflight_batch();
+      return false;
+    }
     g_inflight_active = false;
     g_inflight_count = 0;
     g_inflight_batch_id = 0;
@@ -1193,6 +1253,16 @@ receiver_loop_done:
 }
 
 void loop() {
+  if (SERIAL_DEBUG_MODE && !g_debug_forced_reboot_done &&
+      (millis() - g_boot_ms >= DEBUG_FORCED_REBOOT_INTERVAL_MS)) {
+    g_debug_forced_reboot_done = true;
+    serial_debug_printf("debug: force reboot after %lu ms uptime",
+                        static_cast<unsigned long>(millis() - g_boot_ms));
+#ifdef ARDUINO_ARCH_ESP32
+    delay(50);
+    esp_restart();
+#endif
+  }
 #ifdef ENABLE_TEST_MODE
   if (g_role == DeviceRole::Sender) {
     test_sender_loop(g_short_id, g_device_id);
diff --git a/src/web_server.cpp b/src/web_server.cpp
index 8e37401..d702a47 100644
--- a/src/web_server.cpp
+++ b/src/web_server.cpp
@@ -57,6 +57,32 @@ static HistoryJob g_history = {};
 static constexpr size_t SD_LIST_MAX_FILES = 200;
 static constexpr size_t SD_DOWNLOAD_MAX_PATH = 160;
 
+static String format_utc_timestamp(uint32_t ts_utc) {
+  if (ts_utc == 0) {
+    return "n/a";
+  }
+  time_t t = static_cast<time_t>(ts_utc);
+  struct tm tm_utc;
+  gmtime_r(&t, &tm_utc);
+  char buf[32];
+  snprintf(buf, sizeof(buf), "%04d-%02d-%02d %02d:%02d:%02d UTC",
+           tm_utc.tm_year + 1900,
+           tm_utc.tm_mon + 1,
+           tm_utc.tm_mday,
+           tm_utc.tm_hour,
+           tm_utc.tm_min,
+           tm_utc.tm_sec);
+  return String(buf);
+}
+
+static uint32_t timestamp_age_seconds(uint32_t ts_utc) {
+  uint32_t now_utc = time_get_utc();
+  if (ts_utc == 0 || now_utc < ts_utc) {
+    return 0;
+  }
+  return now_utc - ts_utc;
+}
+
 static int32_t round_power_w(float value) {
   if (isnan(value)) {
     return 0;
@@ -374,6 +400,11 @@ static String render_sender_block(const SenderStatus &status) {
   if (!status.has_data) {
     s += "No data";
   } else {
+    s += "Last update: " + format_utc_timestamp(status.last_update_ts_utc);
+    if (time_is_synced()) {
+      s += " (" + String(timestamp_age_seconds(status.last_update_ts_utc)) + "s ago)";
+    }
+    s += "<br>";
     s += "Energy: " + String(status.last_data.energy_total_kwh, 2) + " kWh<br>";
     s += "Power: " + String(round_power_w(status.last_data.total_power_w)) + " W<br>";
     s += "P1/P2/P3: " + String(round_power_w(status.last_data.phase_power_w[0])) + " / " +