@ricktreze Good day, 

Thank you for your feedback,   here is public driver for Archer T4E and you could give it a try: 

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

If the issue persists, can you help confirm some details to locate the problem, thank you~

• Model number of main router and a photo of 5Ghz wireless settings on router: 
• Does 2.4Ghz work fine with tp-link adapter? 
• When the 5G connection become unstable, is there any Error message or connected but no Interent? How does 5Ghz recover? 
• When did you purchase this adapter and when did the issue start?  
• Please let us know the driver version and motherboard of your PC：https://www.tp-link.com/support/faq/2722/