Loose connection on two shelly devices

Hello
I installed one wifi shelly 1 and a shelly plug. Both work but they loose cyclic the connection. Wifi is stable and by about 4m distance. 5 Ghz is turned of.
Both the shelly 1 and the shelly plug say in log: Service not available, then they come up after some seconds again. I set them to static ip.
An integrated Shelly pm4 with lan works well. Somebody an idea ?

Thank you

Nobody an idea ?