High FC test goes orange/brown

Hi Guys,

Currently Slamming my pool which is normally SWCG. Due to highish cya the slam target is up hugh (was 28, replaced some water to drop cya to target 24)

At the high FC numbers (24+) my titration test turns orangey/Brown at the last drop. More drops do nothing to change the color.

Any ideas? Kit is only a few months old.
 

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