Simplistically, the most recent discussion here which has been very worthwhile, is that an anomaly has been identified whereas BiaB has the ability to control the exact bass note to be played - as long as it is not the same as the named chord.

To explain:
A/B is OK. The required played note by the bass is always B.
A/G is OK The required played note by the bass is always G.
or any other variation.

However:
A/A does not work reliably where the required played note by the bass is A

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