Why is the LAN connection between the Sunny WebBox and the AVM FRITZ!Box sporadically separated?

When using the Sunny WebBox in combination with an AVM Fritz!Box, a LAN connection interruption can occur if the AVM firmware has not been updated. This occurs during the energy saving mode of the FRITZ!Box and can be remedied by a current firmware update of the FRITZ!Box. Once this is done the Sunny WebBox should function without further problems, irrespective of the energy saving mode of the Fritz!Box.

This is not any failure of the Sunny WebBox!