@fishingisme 

Hi, thank you for your inquiry about tp-link range extender.
For the RE dropping-out issue, please refer to this FAQ to troubleshoot at first: https://www.tp-link.com/support/faq/2233/

If still the same issue, can you help us confirm some information:

1. Please let us know the troubleshooting steps you have tried in detail, thank you!
2. How often this issue happens? What about the LED Status on RE when this issue happens?
3. May I know the problem occurs on 2.4G or 5G Wi-Fi?  How long do you have this RE and when did the issue start?

4. The correct model number of the RE. AC750 is not the correct model number.

5. May I know the distance between the RE and the router?

    Did you put RE in very close to router (within)and check stability? What is the model of the main router?

6. If the extender and router have the same Wi-Fi name or different one? Do you have a stable Wi-Fi connection from the main router? 

7. Since you said the extender dropped out completely for a few seconds, how does the internet recover?

By restarting or automatically? If the extender only drops out for a few seconds, can you connect the router's connection to check if it is working well?

8. Can you follow the below instruction to check the IP address, default gateway on your PC which is connected to the extender's Wi-Fi when the issue happens?  https://www.tp-link.com/support/faq/838/

Thank you for your precious time. 

Good day!