diff --git a/zephcore/adapters/radio/SX126xRadio.cpp b/zephcore/adapters/radio/SX126xRadio.cpp
index 5d57b83..df4b3e8 100644
--- a/zephcore/adapters/radio/SX126xRadio.cpp
+++ b/zephcore/adapters/radio/SX126xRadio.cpp
@@ -201,8 +201,15 @@ void SX126xRadio::applyRxDutyCycleIfEnabled()
 		return;
 	}
 
-	uint32_t symbol_us = ((uint32_t)(1 << sf) * 1000) / (uint32_t)bw_khz;
-	uint32_t sleep_period_us = sleep_symbols * symbol_us;
+	uint32_t symbol_us = (uint32_t)((float)(1 << sf) * 1000.0f / bw_khz);
+
+	/* Shave 2 symbols off the sleep period so the wake window always overlaps
+	   with enough preamble for detection, even in the worst-case arrival timing.
+	   Without this margin the math lands at exactly zero — any TCXO drift,
+	   crystal error, or processing latency causes missed packets. */
+	int16_t sleep_symbols_safe = sleep_symbols - 2;
+	if (sleep_symbols_safe < 1) sleep_symbols_safe = 1;
+	uint32_t sleep_period_us = (uint16_t)sleep_symbols_safe * symbol_us;
 
 	uint32_t preamble_total_us = (preamble_len + 1) * symbol_us;
 	int32_t wake_calc1 = ((int32_t)preamble_total_us -
diff --git a/zephcore/patches/zephyr-new/drivers/lora/lr11xx/lr11xx_lora.c b/zephcore/patches/zephyr-new/drivers/lora/lr11xx/lr11xx_lora.c
index b67f44f..64c8db4 100644
--- a/zephcore/patches/zephyr-new/drivers/lora/lr11xx/lr11xx_lora.c
+++ b/zephcore/patches/zephyr-new/drivers/lora/lr11xx/lr11xx_lora.c
@@ -258,8 +258,14 @@ static void lr11xx_apply_rx_duty_cycle(struct lr11xx_data *data)
 		return;
 	}
 
-	uint32_t symbol_us = ((uint32_t)(1 << sf) * 1000) / (uint32_t)bw_khz;
-	uint32_t sleep_period_us = sleep_symbols * symbol_us;
+	uint32_t symbol_us = (uint32_t)((float)(1 << sf) * 1000.0f / bw_khz);
+
+	/* Shave 2 symbols off sleep so the wake window always has enough
+	   preamble overlap for detection.  Without this the margin is zero
+	   and any TCXO drift or crystal error causes missed packets. */
+	int16_t sleep_symbols_safe = sleep_symbols - 2;
+	if (sleep_symbols_safe < 1) sleep_symbols_safe = 1;
+	uint32_t sleep_period_us = (uint16_t)sleep_symbols_safe * symbol_us;
 	uint32_t preamble_total_us = (preamble_len + 1) * symbol_us;
 	int32_t wake_calc1 = ((int32_t)preamble_total_us -
 			      ((int32_t)sleep_period_us - 1000)) / 2;