E020 reference adjustment error

What usually fixes it:

Clean the flow cell and optical window — dried hemoglobin residue is the #1 cause.

Prime/flush the reagent lines — any tiny air bubbles during the reference read will trigger E020.

Check the lamp output — weak/degrading lamp causes unstable reference levels.

Verify the reference cuvette path is seated and not contaminated.

Re-seat the detector board connectors — intermittent optics power can throw this exact error.

If it keeps coming back then the optical assembly is drifting and needs replacement or factory alignment.