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TL431LI: TL431 Unexpected voltage thershold

Part Number: TL431LI
Other Parts Discussed in Thread: TL431, TLV431

With the TL431 circuit below the TL431 diode stops conducting ~3.0V (voltage at J7), but it was expected to turn off at 2.5V + (Iref * R82) = 2.5V + (0.4uA * 1kohm) the voltage drop across R82 is not expected to be significant.

The 1kohm is needed to limit reverse voltage current. 

Any insights on why does the diode stop conducting 3.0V instead of 2.5V?

Thank you in advance for any help.