GRT Avionics

A few times in the last few months, during a flight, the data file with engine and flight data 'GRT Flight Data Log.CSV' has had what looks like binary data written to it. The binary data can be written to the file for over an hour, and then it stops and normal text logging of the engine and flight parameters resumes. I have not been trying to record a demo flight, so I don't think that is the issue.
Any pointers? Right now I am having to manually strip out the binary data from the file and deal with the loss of the flight data that I want to analyze.

Thanks,
Byron

In my experience this usually means the file or filesystem got corrupted, not that that the EFIS actually tried to write that. I would check the drive for errors to make sure all data blocks are marked properly (the quick check, not a full block scan). This can be done with the drive Properties on some computers. Or you can remove everything from the drive and do a quick reformat but make sure it stays in FAT32 format.