It happens quite often, 3 times a day at least. Whenever it does i can see that my local wifi appears saved & ready but it won't reconnect until i restart my TV.
The tv like every device in our house (PCs, Console, Printer..) set with static IP.
I've seen similar posts with no actual solution.
I had so many issues with my Sony Bravia I just bought an Nvidia Shield instead. Zero issues since.