I think that this change of incubation turns was strategically planned- Kaia in the nest at night, leaving the hatching process to Karl...
Quoting Marika's post:
"The young mostly hatch through the male during the hatching, as only the female is able to give the young small portions of the possibly large prey pieces in the first few hours after hatching. Therefore, the female goes in search of food during the hatching phase, in order to then carry out the first feedings herself."
(p. 215-216 in Janssen, G., M. Hormann & C. Rohde (2004, 2013): Der Schwarzstorch. Neue BrehmBücherei 468. VerlagsKG
Wolf, Magdeburg)
https://ciconianigra.sk/viewtopic.php?p=2957#p2957