I did spend few days trying to solve a very strange problem with 50 Wemos D1 boards I purchased for a project.
They disconnected from the USB and WiFi, had very high ping times and high current consumption (and heat!)
The ESP12 come from doit.am. I you have the same problem with the same manufacturer maybe this can help you:
https://geekenargentina.wordpress.com/2019/10/08/esp8266-connectivity-troubleshooting/
regards,
Román