Deep Sleep on Fipy - no wake up

[apiwize]

Hi all, I face problems with fipy, firmware up to date, wether connected on expansion board or to any pcb. Whel I call deep sleep, the machine goes into deep sleep... but never wake up.
Same configuration is OK with lopy4.
Any idea ? Thanks for your feedback !
Sample of code used (need a "time.sleep" prior to deepsleep to enter properly in deep sleep, but it changes nothing on fipy problem)

def deepsleep(self):
	time_ms = self._time_to_sleep()
	output("going to sleep deep for {} miliseconds".format(time_ms if time_ms else 'infini'))

	flash(white, 2)

	time.sleep_ms(400)
	machine.deepsleep(time_ms)