The obvious word which means 'given to inconsistencies,' would be 'inconsistent'.
According to my dictionary, inconsistent is an adjective meaning to contain "conflicting or contradictory elements," or something which is "not in agreement."
- inconstant: "likely to change without apparent reason."
- erratic: "lacking consistency or regularity; unpredictable."
- fickle: "inconsistent in one's loyalties."
- capricious: "changing mood suddenly or unpredictably."
- mercurial: "having constant changes of mood."
You may also want to check out an online thesaurus like the one at http://www.thesaurus.com/ when looking up words that have similar meanings. If none of the words above are quite what you're looking for, then this is a sure fire way of discovering some new words you may not have considered.
In this film, the word 'inconsistent' is examined in relation to the world of dating. I found this pretty funny!