Every time only 14sec data is saving in SD card (But I am doing experiment for 15mins)

I am facing an problem in getting an data from the SD card.
I am doing an experiment in which i am calibrating an GPS and RTK-GPS (Doing separately, one by one). I am turning on the power and then ARM the system. Then I will wait for 15mins to get the data. Then I DISARM the system and then disconnect the telemetry and then switch off the power and then read the SD card.

The SD card in Pixhawk having the .bin file. When I extract the .bin to .matlab file I am seeing that every time I am getting for the time period of 14sec only and rest data points is not coming. (But experiment has done for 15mins)

Can anyone please solve this problem. How I can solve this issue???..

I have also used new SD card but same problem I am facing… Please help in this…

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