Obviously its been decades since I've seen an L1011 ...
Quite likely the problem, then...
Newer build aircraft and those so modified via service bulletin incorporated a comparator/resolver in the ADF system, to indicate a reversed sensing condition.
It caused a flag to appear in the respective RMI indication.
However, it did not resolve another problem that is common with ADF receivers in general.
If the broadcast signal 'goes away' due to equipment failure on the ground, no flag will appear, so it is quite necessary to have one crew member monitor the audio continuously, during an NDB approach.