The SWI Prototrak Plus DRO is a CNC axis read‑out system that uses an optical encoder wheel to provide 3‑axis dimensional feedback. Common failures include the encoder wheel stalling when chips or debris accumulate between the wheel and measuring surface; this is often caused by worn foam inserts (replaced twice yearly) or metal chip scrapers that need periodic cleaning or replacement. Another frequent issue is loss of zero datum on startup, typically due to residual program memory or incorrect G‑code formatting for the SWI MX2 post processor. First‑check diagnostics: verify power and signal integrity to the encoder board, inspect and clean the measuring wheel and foam inserts, and review stored programs or error logs for zeroing commands.[oss-gpt-20b]