During all the test something happen which remind me to another Bug report. I opened the web interface for a longer time and in addition the IOBroker connects every 240 seconds over the WEB API. After some time, the device frozen completely. My switch reported - still connected, access with ping and telnet isn't possible anymore. This happened around 3h. I reboot the device and closed the browser window. Currently it runs stable for around 20hours.
As reported by @Helmut1965 in https://github.com/emsesp/EMS-ESP32/discussions/2228#discussioncomment-11332852_