IF functions not calculating

I have a series of IF functions calculating on the basis of certain cells. Eg:

=IF(BBR54=".",".",IF(AND(BBR54="1",BBR56="1"),"1",0))

On checking the results, I have found that for certain columns, some of the calculations are NOT calculating. That is, if the IF calc criteria are met, I'd expect a '1' returned, but sometimes it isn't. However, if I input '1' into the source cells, then the calculation works as expected.

I have tried using source/calc cells as numbers or as text (as in the calc above). Neither always works. Lastly, I have tried copying source cells and pasting them, but no improvement.

Any ideas?