Centaurus,
Interesting. Do we know whether both ADFs were tuned to the same NDB. I do not know Bali and I do not know what other aids would have been available or needed. For example, did the procedure require another NDB to be tuned as well? If both ADFs were tuned to the same NDB, I would have been very wary of only one needle swinging round.
Also, do you know more about the weather at the time? Although the sky was reported to be clear with the stars bright and the sky moonless, presumably that was at the airfield. Were there any active Cbs close to where the needle swung and they turned onto the new heading? I have certainly seen ADF needles point to a Cb instead of the NDB.