Error: Don't use RTC mem data...

Hi,

One of ESP8266 in our hands is not working while throwing the only message upon boot like the following:

e0\0x0c\0x0c\0x0c\0x0cb\0x0cn\0xe2|\0x02­\0xec\0x8e\0x8e\0x8eb\0x8c\0xf2nn\0xee\0­x00\0x0c\0x8el`\0x02\0x90\0x12\0x12nn\0x­0c\0x8e\0x0el\0x0e\0x02nr\0x8e\0x92\0x92­n\0x0c\0x0c\0x92\0x02l`\0x02p\0xf2n\0xe0­\0x10\0x02\0x0c\0x0cr\0x8c\0x9c\0x9c\0xe­2\0xe0\0xec\0x0c\0x0c\0x0cb\0x0cn\0xe2|\­0x02l\0x8e\0x8e\0x0cb\0x8c\0xf2nn\0xee\0­x00\0x0c\0x8el`\0x02\0x90\0x12\0x12nn\0x­0cl`\0x02\0x0e\0x02nr\0x8e\0x92\0x92n\0x­0c\0x0cr\0x02l`\0x02\0x0er\0x92\0x92n\0x­0c\0x0cr\0x02l`\0x02rl\0x8c\0x8cn\0x9c\0­x8c\0xf2nn\0x9e\0x8c\0x9e\0xe2\0x8cr\0x1­2nnn\0x8c\0x0cl\0x8cb\0x8ebp\0x82lb\0x0e­l\0x00\0x0c\0xec\0x12\0x92l\0xec\0x12\0x­92\0x92\0x82\0x02\0x0c\0x0c\0x0c\0x0c\0x­0c\0x8c\0x0c\0x0c\0x8elll~rl\0x00\0x0c\0­xec\0x12\0x92llln\0x9c\0xe2\0x00\0x0c\0x­0c\0x0c\0x0c\0x0c\0x0c\0x8c\0x0cl\0x92ll­\0x0el\0x00\0x0c\0xec\0x12\0x92l\0x8c\0x­90n\0xe0\0x8e\0x02n\0xec\0x92n~\0x12\0x0­2\0x8c\0x8cll\0xe0\0x80b\0x0c\0x0c\0x8e\­0x8e\0x0c\0x12n\0x9eb\0x1c\0x92\0x8c\0x8­eb\0x0crb\0x1c\0x92\0x8c\0x8eb\0x0c\0x12­b\0x0ell\0x92\0x92n\0x02\0x0c\0x9en\0x8c­\0x92\0xe2nl\0x9e|\0x12b\0x12\0x0c\0x0c\­0x02l\0x0c\0x0c\0x0cl`\0x02rldon't use rtc mem data

The last sentence, don't use rtc mem data might give a clue but it's meaningless for me. What would it be?