It seems that 61F's Floatless Level Controller electrodes are dirty and sensitivity has dropped. How?

Tarnish on the electrodes will cause poor conductivity.

Polish the electrodes with an abrasive such as fine sandpaper.

Use a cloth to wipe off the residue.

The electrodes are stainless steel, so it is also acceptable to use a commercial chemical cleanser, but be sure that the liquid in the container is not affected. If the electrodes are extremely dirty, it may be necessary to replace them.