Wrong IP-Address after reconnect

Hello from Hamburg,
i use a Arduino Nano 33 IOT and a Raspi 4 as Local Server.

the first connection works fine. but if the arduino lose the connection, it uses a wrong IP address for reconnect. for example: the Server-IP is but if the Arduino reconnect, then it uses a totally diffrent IP.

is this a Problem of my Sketch, or a problem of some other files ?

Difficult to say without seeing your sketch.