excel "IF" formula returning "0" (it shouldn't)

Question

Here's the formula

=IF(
    AND(
        NOT(ISERROR(Table3[[#This Row],[lot_ID]])),
        Table3[[#This Row],[uniquness]]="unique"
    ),
    LEFT(Table3[[#This Row],[lot_ID]],3),
    "junk"
)

Below is the formula evaluation (some middle steps omitted. The last two contain the puzzle.)

The mystery has really got me.

Answer 1

I had exactly same problem.

Turns out I had a circular reference that was messing things up. I solved it by

1. going to Formulas tab ->
2. Formula Auditing ->
3. Error Checking ->
4. Circular references

It showed me the exact cell that was a circular reference. Once adjusted everything started working as expected.