Identifying the Problem: The initial ink depletion issue after few but infrequent prints might have stemmed from excessive head cleaning. Subsequently, despite installing non-genuine replacement cartridges labeled as LC 51, compatible with the original LC 37 cartridges, the printer continues to report the Black cartridge as empty, despite being half full. Moreover, it also indicates low ink levels for color cartridges, despite being more than half full.

Troubleshooting Steps:

1. Verification of Cartridge Compatibility: Confirm whether the non-genuine replacement cartridges (LC 51) are indeed compatible with the printer model (MFC 235C). Ensure the cartridges are securely installed and seated correctly in their respective slots.
2. Resetting Ink Levels: Attempt to reset the ink level indicators on the printer. This process varies depending on the printer model. Consult the printer's manual or online resources for specific instructions.
3. Cleaning Cartridge Contacts: Clean the contacts on both the printer and the cartridge to ensure proper communication. Use a lint-free cloth lightly dampened with water or isopropyl alcohol to gently wipe the contacts.
4. Firmware Update: Check if there are any available firmware updates for your Brother MFC 235C printer. Sometimes, firmware updates can address compatibility issues and improve printer functionality.
5. Performing Printer Maintenance: Execute a thorough printer maintenance routine, including nozzle cleaning and alignment. This process can help resolve printing issues caused by clogged nozzles or misalignment.
6. Contacting Brother Support: If the issue persists after attempting the above steps, consider reaching out to Brother customer support for further assistance. Provide detailed information about the problem encountered and the troubleshooting steps already taken.

Additional Considerations: It's essential to acknowledge the potential risks associated with using non-genuine or refilled cartridges. While they may offer cost savings initially, they can sometimes lead to compatibility issues or poor print quality.

In the event that resolving the cartridge issue proves unsuccessful, it may be worth evaluating the overall cost-effectiveness of continuing to use the printer versus investing in a new one. However, before resorting to drastic measures, exhaust all available troubleshooting options.

Resolving the persistent empty cartridge issue on the Brother MFC 235C printer requires a systematic approach encompassing verification of cartridge compatibility, resetting ink levels, cleaning cartridge contacts, performing firmware updates, and conducting printer maintenance. If all else fails, consider seeking assistance from Brother support. Remember to weigh the long-term cost implications and consider the viability of investing in genuine cartridges or a new printer.