There might be several problems:
- You may want to try an other SD-card formatted properly (FAT32, 4096 Bytes, max. 8 GByte) iot avoid reading problems that could ruin your prints.
- You may want to dismantle & clean up your extruders. If that grinding still remains you’ll need to unscrew the nozzle, align it with the heatbreak using the cleaning needle & screw it tightly.
- After changing/fixing the nozzles it is neccessary to adjust Z-offset & align both nozzles again.
Good luck!