@Dale19 

Hello, 

Generally, the clients will choose better and stronger signal wireless automatically and we cannot change their choice by changing settings on the extender.

If you want to connect the device to the main network when there is a stronger extender network, you may try to change the extender network to a different SSID and connect to the main network manually in some locations as the extender signal is stronger.

For a wireless device roaming issue, you may refer to this FAQ below:

https://www.tp-link.com/support/faq/592/