Modbus Request and response Missing.

Dear all.

I have Used modbus RTU library from below link.

The code seems working fine for me.I am sending request for every 30S . I can in serial monitor the request has been gone But there is no valid response sometime. Kindly refer the Image attached below.
What need to be done to avoid missing of response. I have also attached my code and library link below.

With using Below library is it possible to get response only when request has been sent. In current situation I can able to track how fast data has being saved into buffers.
Your suggestion are appreciable here.

glob.h.pdf (46 KB)

Modbus code.pdf (6.01 KB)

Why post the code as PDFs ? You know better than that.