How to Write to SD Card at high rate?
OK. I take back my earlier comment. You do have an electronics issue. What you failed to mention in your question but is visible in the link you have now provided is that when you get multiple files the names are gibberish, they are the result of file system corruption rather than something actively creating files.

This is happening because you are not supplying sufficient power to the SD card. When you perform a write the current draw of the card jumps up rapidly, if the power supply is insufficient this causes the voltage supplied to the card to dip temporarily causing the write to fail and corrupting the file system. This shows up as random gibberish files/directories being created or sometimes the entire card becoming unusable and requiring a reformat.

Check your wiring and verify the SD card is getting a good solid 3.3V supply with low impedance connections from the socket to the power supply. Adding extra capacitance to ground right on the power pin of the SD socket will also help.