@jmarcelino Yes, my problem is the same as what you highlight, thanks for solving the mystery. As an temp solution (for lazy ppl) I can suggest : # hard reset if last was a soft reset if reset_cause() == 4: reset() if not 'sigfox' in locals(): sigfox = Sigfox(mode=Sigfox.SIGFOX, rcz=Sigfox.RCZ4) Regarding the UART1 activity causing Sigfox instability, I will do more tests later. Maybe update the SiPy pinout PDF to include the UART1 pins (like LoPy) as @livius mentioned?