diff --git a/BLE/DLD110S_Peripheral_28K/APP/peripheral_main.c b/BLE/DLD110S_Peripheral_28K/APP/peripheral_main.c
index 42a64b0..1c2cbc5 100644
--- a/BLE/DLD110S_Peripheral_28K/APP/peripheral_main.c
+++ b/BLE/DLD110S_Peripheral_28K/APP/peripheral_main.c
@@ -609,12 +609,18 @@ void vd1_task(void){
          *================================================================*/
         loop1_dlt_ORG = ((uint32_t)loop1_Origin * g_loop_sens_list.sens[g_freq_sens].sens_in) >> 16;
         {
+            /* V4B V4.20 同步: 双向对称保护 — 负variation(铁块磁导率)也冻结基线
+             * 原单边只挡 dev>+4×dlt, 负variation会把Origin污染抬高 → 离开时假进入 → 锁死不释放
+             * 修复: ① 对称窗口 [-4×dlt, +4×dlt] ② 负偏差只冻结永不超时更新 */
             int32_t dev = (int32_t)loop1_CAPVD - (int32_t)loop1_Origin;
-            if (dev < (int32_t)(loop1_dlt_ORG * 4)) {
+            int32_t freeze_band = (int32_t)(loop1_dlt_ORG * 4);
+            if (dev < freeze_band && dev > -freeze_band) {
+                /* 对称窗口内 → 正常基线跟踪 */
                 loop1_freeze_cnt = 0;
+                loop1_freeze_ref = 0;
                 update_moving_average(&loop1_ORG_SUM, &loop1_ORG_CNT, &loop1_Origin, loop1_CAPVD, WINDOW_ORIGIN);
-            } else {
-                /*--- CAPVD 异常偏高: 暂停跟踪, 冻结超时 + 稳定性双条件 ---*/
+            } else if (dev < 0) {
+                /* 正variation (疑似车) → 冻结, 保留超时兜底更新 */
                 if (loop1_freeze_cnt == 0) {
                     loop1_freeze_ref = loop1_CAPVD;
                 } else {
@@ -633,6 +639,15 @@ void vd1_task(void){
                 }
                 loop1_ORG_CNT = 0;
                 loop1_ORG_SUM = 0;
+            } else {
+                /* 负variation (CAPVD高于Origin, 特殊铁块磁导率主导) → 只冻结, 永不更新 Origin */
+                if (loop1_freeze_cnt == 0) {
+                    loop1_freeze_ref = loop1_CAPVD;
+                }
+                loop1_freeze_cnt++;
+                if (loop1_freeze_cnt > FREEZE_TIMEOUT) loop1_freeze_cnt = FREEZE_TIMEOUT;
+                loop1_ORG_CNT = 0;
+                loop1_ORG_SUM = 0;
             }
         }