@leopoldo1878 

Theoretically the powerline adpaters won't affect the performance of the main router; we will do some troubleshooting first to locate the issue and try to fix it.

1. What is the light status of the powerline adapter when the connection drops out?

Please click here to check the IP address and default gateway with your device connected to the powerline adapter.

2. Meanwhile if the main router stops working, please connect computer to the router directly and verify its IP and gateway as well.

Note: please show us the screenshots of the status-details page.

3. Try to change another power socket to plug them or hard reset them by holding the reset button/hole for 10s, after that, please test the performance.

Meanwhile, please ensure that the firmware of TL-WPA4220 is up to date. 

4. Besides, you can refer to the instruction below  to narrow down the root cause. 

https://www.tp-link.com/support/faq/2230/

Any updates, please let us know.

@leopoldo1878 

Thanks for your reply, glad to hear that a reset works;

You can take more time to test its performance and stability.

Any updates, please let us know.