FDM 3D Printer Repair Expert Needed

I need a skilled technician to diagnose and repair an FDM 3D printer that is currently printing air.

The following troubleshooting steps have already been attempted without resolution:
- Checked filament feed and loading
- Checked for clogs in nozzle
- Calibrated the printer bed
- Extruder and hot end replaced

Ideal skills and experience:
- Proficiency in diagnosing and repairing FDM printers
- Strong understanding of printer mechanics and electronics
- Experience with troubleshooting print quality issues

Looking for a detailed diagnosis and effective repair solution.