It sounds like the Sense Antenna for one of your ADF's is faulty.
I've been told that the Loop Antenna can df without the Sense Antenna, but only if the signal is good.
You didn't specify what type of aircraft you have. For each ADF system, some aircraft have separate sense and loop antennae. Other aircraft have combined sense and loop elements in the same antenna.
On our Classic 747's, the sense antenna connection was a single black wire attached to an antenna embedded in the wing to body fairing panels. It was easily broken.
Did your maintenance department correct the problem?
Rgds.
NSEU