Incompatibility, incongruity (13)
I believe the answer is:
inconsistency
I believe this is a double definition.
'incompatibility' is the first definition.
(I know that incompatibility can be written as inconsistency)
'incongruity' is the second definition.
(thesaurus)
(Other definitions for inconsistency that I've seen before include "Discrepancy" , "Variability (of opinion, performance)" , "Disparity" , "Inherent self-contradiction" .)