Hi!

Short of a defective PG detection circuit, it's very possible you
could have some weak caps that are not totally filtering correctly
and the circuit see's a little switching noise.

It would surprise me (only a little, so you know my expecations have
been lowered) to find something brand new coming out of the box with
bad caps.

I don't know what might have caused it. The supply seemed to have
excellent regulation on all other outputs. All of the 3.3, 5 and 12
volt leads tested fine. In any case, I traded it off for a new supply
under warranty and that one happens to work.

William