Thanks for the hint. Yes, it would solve the problem but would at least triple the the size of my controller
Just wanted something smaller/simpler/(cooler?) then what m using now: Raspi-Zero with a relay module.
The problem solves a capacitor of 470 uF on the optocoupler on the relay board. It is just not nice, a workaround a bug in the ESP-8266-01's firmware:-(
I would prefer to have the firmware fixed but for a mere mortals i.e. private users it's impossible to file a bug.
I have the impression, you didn't read carefully description of my problem.