Expert 3D Printer Fix

I have two printers, a Voxel Monoprice and a Longer, that need professional diagnostic and repair services. Here's a breakdown of the issues and what I'm looking for in a freelancer to help resolve them:

- Voxel Monoprice:
- Uneven/rough print surface
- Possible over-extrusion and small layer shifts.
- Likely needs recalibration or other adjustments.

- Longer 3D Printer:
- Calibration and leveling issues.

No error messages are being displayed on either machine, suggesting that the problems may be mechanical or calibration-related rather than electronic. As a result of the issue - inability to remove supports ( Monoprice) or adherence issues on Longer.

Ideal Freelancer Skills:
- Experience with Voxel Monoprice and Longer 3D printers.
- Mechanical aptitude for diagnosing and fixing uneven print surfaces.
- Proficiency in calibrating and leveling 3D printers.
- Ability to resolve extrusion and layer shift issues.

Please provide a brief overview of your experience with 3D printer repair, particularly with the listed models, and your approach to fixing such issues. I am looking for someone who can get these machines back to their optimal printing quality.

Thank you for considering my project!