Issue reading and writing file on a USB flash drive

Official Hardware Mega GIGA R1 WiFi
2

I know in the one sketch that I used to read files from USB drive, I had code in it like:

      if (!msd.connected()) {
        if (msd.connect()) Serial.println("MSD Connect");
      }
      if (msd.connected()) {

That is, you don't try to do a connect if the drive is already connected.

You might try something like that to see if that helps or not.