Wifi issues with iPhone

Ok so my iPhone was great, until I installed iOS 11.4.1. Since then the wifi kept cutting in and out. I've tried everything I can find, such as resetting network setting, forced restart, forgetting network and reconnecting etc... I tried rolling back to 11.4 as I'd had no issues before. But it forced the recent update again. I can't find a signed version to roll back to now other than the 11.4.1. So I've installed iOS 12 beta version 3 (current version at the moment) And the wifi connection seems to last longer, but eventually cuts off and only reconnects after toggling wifi off and on again.

Does anyone know a real solution to this, or has Apple decided to break my phone?