Receive data is not stable

[CpH777]

My port setting is this
String? portName;
String? baue = '38400';
String? parityBits = 'NONE';
String? dataBits = '8';
String? stopBits = '1';
String? streamCtrl = 'NONE';

My receive handler is this

void receiveISR(SerialPort port) {
final reader = SerialPortReader(port);
reader.stream.listen((data) {
tempList.addAll(data);
receDataTodo();
tempList.clear();
}, onError: (Object error) {
print("ERRORRRRRR");
});
}

receDataTodo(); to do thing is save receive data to a csv file.

and i fine this phenomenon

but i check hardware to send is ok

i can't Explain this phenomenon，can you give me some advice?

[CpH777]

i lose some data during receive data like the picture

[Arvinth-Krishna]

the text I selected is one single string from the motherboard but here it got separated into multiple lines.

can you please tell me if there is any option to increase the buffer size?

[Arvinth-Krishna]

This is the text coming from the motherboard.

I want this entire line. Can u pls help how to do that?