There are several things to check:
1. do you have a single WiFi router or you have WiFi range extenders / mesh network at home?
2. Note that we just released a newer version of firmware 2.1.8, which uses the latest ESP8266 core library and should have improved WiFi functionality. For OS 3.0 users we recommend upgrading to firmware 2.1.8.
3. You can submit a support ticket to arrange for a replacement controller to be sent to you.
As a last resort: please note that we still sell version 2.3, with built-in Ethernet — the Ethernet version still exists, it’s not gone yet.