Hi,
I have the same issue : according to my router, my freedombox disconnected from my network the same night as yours, around the time for auto-upgrade I believe. So I think it is an issue with this update indeed.
I am using an A20-OLinuxino-Lime2. Do you happen to use the same device ?
I think there has already been a similar issue, where a bug affected a specific revision of this board.
EDIT: the previous bug Lost all access to FreedomBox (I don’t know if it’s the same thing happening again, since the symptoms are quite generic).