Maybe it is a software problem in the BSS… When you deleted this adjacency, it should not be seen in the SI5 and SI2 messages.
Those can be seen in the Layer-3 messages from your NEMO. When looking at those SI messages, do you still see the BCCH frequency of the neighbour ?
If yes : then the BSS software is not working properly.
If no : then NEMO is smarty.