It seems to me that in the recent past I had an issue with the wifi on my 740. It only happened once, and I've not seen any reason to try and replicate it but FWIW, here's what seemed to happen:
I think I started the 740 before I started the plane and therefore the ADSB/wifi. After flying for a while I noticed that I wasn't getting any ADSB signal, so I went through the process to reconnect to the ADSB. I tried that several times with no success. I tried both automatic, and selecting my specific device the Stratus 3. Finally I tried exiting iFly, leaving it running in the background. When I checked, the 740 was not connected to the wifi. I had it connect to the Stratus 3, resumed iFly, and the ADSB connected right up. Thinking back, I thought I saw some messages that I either dismissed, or were dismissed automatically. This led me to surmise that the base OS program tried to connect some small number of times, had no luck, and gave up.
I don't know if this has anything to do with the discussed issue, or if it even actually happened, like I said I wasn't paying close attention to the 740 at the moment. But I guess I've been lucky that I don't recall any issue with wifi connections, although I probably only connect to two or three networks.