I think I have found another bug in the Android-6.0-based OS. My Wi-Fi symbol has an exclamation mark on it every morning. And there is a network type indicator („3G“) next to the mobile network symbol, normally, it is only there when the mobile data is used.
I do not have this issue, but two things would be interesting: Is your phone connected to a charger at night? And does it still have (an) IP address(es) in the morning? (You can check in Settings / Wi-Fi / Advanced.)
By the way: I think my phone didn’t get a IPv6 address in my WiFi until I fixed the issue. Might be related, but I didn’t look at it all the time. Maybe you can check that.
OK. In the last days, I had not this problem. But today, it occurred again. I have looked after the IP address, and there stood “Not available” instead of an IP address.
Do you regularly switch off your router or does it run 24/7?
If the latter is the case I’d suggest restarting it to give the dhcp server the chance for a clean startup.
Good luck.
I see exclamation marks on the wifi symbol only when the network address setup routes and all are not completely finished yet. There are different layers in the networking.
So, my wild guess would be that the DHCP lease expires during the night. Of course the phone should renew it automatically, but that might somehow fail.
What is your DHCP lease time? You can check in Checkup / Wi-Fi. It should be several days.
I had a similar problem with ! on my data SIM, which went away after I “reset network settings”. It’s been much better since then (although I have had to set up networks again, of course)