Exception while running on ESP-8266 but not on Arduino Uno

Hi, While running the code on an ESP-8266, the AZxxx command generates an exception:

Exception (28):

epc1=0x402015a7 epc2=0x00000000 epc3=0x00000000 excvaddr=0x00000000 depc=0x00000000

This is not the case with ELyyy command.

Plus, sending AZxxx ELyyy command works fine.

The exception occurs only when only an azimuth is requested.