loosing crons

hi there,
i just wanted to share an effect i noticed recently,.. from time to time, about all 3-5 days my installation looses one of my three manual php crons.
i use four manual php crons but sometimes one of the hooknames disappears and does not run, so i have to re-add it.

my host is wpengine, rest works fine, crons run, everything nice, except the disappearing from time to time

any idea on that?
br, eric

https://wordpress.org/plugins/wp-crontrol/