The "gesture" option "during sleep" has been removed in a previous firmware, but it was disabled by default.
Now, with last firmware, it has been re-enabled by default without any means to disable it. WHY ???
It is very very annoying for people like me who already have difficulties to sleep already to also get flashes from the watch every time I change position in the night (which is very often ...).
@Garmin, please allow again this configuration.