Failing ESP8266 Socket-Switches

Hello

i had 4 Sonoff S20 and 4 of the sockets from german hardware chain OBI.
The OBI-sockets and one of the S20 stopped connecting over time.
First they randomly lost connection and reconnected until the reconnect stopped happening.

Does anyone else experienced behavior like this?

A friend suggested this:
non-working ESP8266 are usually because of brown-outs, so soldering a capacitor into it could solve that problem.

My own alternative would be trying to connect via a FTDI and erasing at least the firmware and the Eeprom before throwing them away.

Any ideas? Suggestions?

really? are my sockets the only one dying?