Forced sleep reset during sleep mode.

[smc3534]

I'm testing it with an OTTA example. appTxDutyCycle is 15 seconds, class A mode. data sending and receiving
It goes into deep sleep mode and wakes up to RST again within 3-5 seconds.
Below is Serial log.

---------------------------------------------------------------------------------------------------------------------------------------------RX on freq 922100000 Hz at DR 5
DIO0:RX Done
joined
vibration data collection ok
confirmed uplink sending ...
TX on freq 923300000 Hz at DR 5
Send
DIO0:TX Done
RX on freq 923300000 Hz at DR 5
DIO0:RX Done
receive data: rssi = -93, snr = 26, datarate = 5
+REV DATA:RXWIN1,RXSIZE 4,PORT 2
+REV DATA:00000000
vibration data collection ok
confirmed uplink sending ...
TX on freq 923100000 Hz at DR 5
Send
DIO0:TX Done
RX on freq 923100000 Hz at DR 5
DIO0:RX Done
receive data: rssi = -94, snr = 24, datarate = 5
+REV DATA:RXWIN1,RXSIZE 4,PORT 2
+REV DATA:00000000
Deep Sleep until Next TxPacket:13789 ms
ets Jul 29 2019 12:21:46

rst:0x5 (DEEPSLEEP_RESET),boot:0x17 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1044
load:0x40078000,len:8896
load:0x40080400,len:5816
entry 0x400806ac
Initializing I2C devices...
vibration data collection ok
confirmed uplink sending ...
TX on freq 923300000 Hz at DR 5
Send
DIO0:TX Done
RX on freq 923300000 Hz at DR 5
DIO0:RX Done
receive data: rssi = -95, snr = 26, datarate = 5
+REV DATA:RXWIN1,RXSIZE 4,PORT 2
+REV DATA:00000000
Deep Sleep until Next TxPacket:13793 ms
ets Jul 29 2019 12:21:46

rst:0x5 (DEEPSLEEP_RESET),boot:0x17 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1044
load:0x40078000,len:8896
load:0x40080400,len:5816
entry 0x400806ac

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Do you have a Hw pin that makes it wake up? Or is there another reason?

Thanks.