See attached ...
On the "simplest" inputs, the NaiveBayes Method with Classify produces different outputs for the same inputs.
Answer from a closely related post ... etienne bernard added: Hi Mark, as you suspected in the notebook, this behavior is observed when there is a tie. When the most likely classes have the same probability (or more generally the same utility), a RandomChoice of these classes is done. To avoid this behavior you can use the undocumented options "TieBreakerFunction" and put any function you like. For example "TieBreakerFunction" -> First will give a determinate result.