I too have been having difficulty connecting to all of my wifi since the last update to 14.3. When the phone goes to sleep and I reawaken it, the wifi is not joined like it always has. It takes a while for the available wifi possibilities become available and then I have to pick which one to join. Once I join it stays connected as long as I am using my phone but if it goes to sleep the problem recurs upon be reawakened . I hope apple is aware of this problem so they can fix it.