After some days of testing I think the reason is located with the WiFi reconnects.
As posted above I'm runing three nodes with the 0630-version.
These nodes were resetted by WD after a few hours.
The following steps made them working far more stable:
Usually I run a Ubiquiti Unifi Long Range AP for severeal WiFi's and about 35 devices from TV to ESPEasy.
I disabled the WiFi for home automation on that AP and grabbed an old TPLink AP from the basement shelf
so all nodes are running on a separate AP now.
Secind I set the configuration to "Force WiFi No Sleep"= on and "Periodically send Gratuitous ARP" = on (should be set by default).
Sadly we had a complete power outage here so the uptimesare shorted but atm I have uptimes of around 7 days on all three devices.
I didn't see such uptimes for a while...
I won't say this is a solution.
But it shows quite clear the reason for WD resets is located in the WiFi part, I assume inside the core lib.
Have a nice weekend everynone.