@Fede411 Hello, 

Sorry for the late response, it is recommended to reinstall the latest driver on official driver for T4E.

If  your driver is the latest one, here is a chipset driver which you could give it a try: 

https://static.tp-link.com/2019/201911/20191128/T4E.zip

May I know does the issue happen on 5Ghz or 2.4Ghz, if the issue happens on certain band you could try a different wifi channel on main router. 

If the same problem, may I know the model of your router, does the unstable issue happens on 5Ghz /2.4Ghz band.

Do you have a stable connection if you put other devices at the same location as the T3U computer.

If there any Error message when issue happens, may I have a photo of it. Do you need to reconnect wifi or Internet connection recover by itself? 

 Can you share us  photo of the driver date & motherboard info, thank you.

https://www.tp-link.com/support/faq/2722/