Problem with fc16 using Nmodbus

I have a program developed in .net using nmodbus. This software basically communicates with instruments on the field and captures the data using modbus. Now the problem is...it works fine for a few days even for a week, then it suddenly throws the following error while trying to write the following values into the holding registers

My reg. address is 262 with base 0
The data value is 731

System.ArgumentOutOfRangeException: Maximum amount of data 127 registers

Can anyone tell what am I doing wrong?

Thanks in advance