Read bytes problem in RS232

Hi everybody

I have a device. This device has been designed to send a data stream which is 47-byte in every 100 mSec without any command.

When I begin to read the datas, I read 47-bytes data stream at the bytes read terminal of VISA Read function. But a few seconds or minutes later, it goes crazy. I mean it is raising up to for example 230 byte or falling to 17 byte.

Any idea or help please??   (By the way, I am using "Bytes at port" proporty node before read function)