Hm, another thing you could try is to Reset all settings. Though, you’ll have to set up a lot of stuff again if you changed stuff in the settings.
Otherwise, redoing your iPad might be your best bet. You can backup your device first of course.
If THAT doesn’t work, then it’s a hardware problem and you’ll have to get it fixed by Apple.
I did have a little disconnecting problem with my 5Ghz band Wifi , but the later iOS 11 updates fixed it.