The problem seems to besolved solved.
The range 12288 to 24575 is Modbus-address. I don’t kow why, but apparently rapid scada divides 1, so that scada address 1 appears as standart Modbus-address 0. I set the offset to 12288 so I requested data from standart address 12287. This is a reseved range with no valid data. This seems to be the reason for the occured error.