An OCD-afflicted photog wins over an energetic creative through her awkward yet relentless affection, but as their relationship develops, it becomes too much.

Good points and examples by Nir.

A character who suffers from OCD at the beginning of a film will also suffer from it at the end no matter how the story ends? -- there's no character arc to be had on that character issue.? It's a cognitive disorder that a character cannot intentionally "overcome".? However, he may use his disorder to rationalize morally reprehensible behavior, to con others (and? himself) into excusing his? bad decisions.? And that rationalization/con is the raw material for a character arc.

Good points and examples by Nir.

A character who suffers from OCD at the beginning of a film will also suffer from it at the end no matter how the story ends? -- there's no character arc to be had on that character issue.? It's a cognitive disorder that a character cannot intentionally "overcome".? However, he may use his disorder to rationalize morally reprehensible behavior, to con others (and? himself) into excusing his? bad decisions.? And that rationalization/con is the raw material for a character arc.

"... but I think it's okay to have a character flaw that's not necessarily a flaw in moral character..."

No it's not.

You want your hero to overcome a negative aspect of their character. They can have OCD, as DPG pointed out, it could be a good source of conflict, but they would need to have better themselves in some other way. As Good as it Gets, is a good example in this case - the main character has OCD and is also a short-tempered bigot who hates gay men. By the end of the story, he would have overcome his dislike of gay men but his OCD still remained. This makes his OCD an obstacle standing in his way, not a character flaw. Much the same with Matchstick Men, Nicholas Cage's character was a con artist who suffered from OCD - he was self-centered and morally corrupt, so he needed to learn to be a better person throughout the story. His condition was used as an obstacle that created conflict but by the end of the story, he learns his lesson and stops being a con man through fatherly love (all be it fake)? - that was the emotional payoff of the story.

Character flaw aside, the wording in the logline is confusing and the goal is not clear. You wrote that he "...wins over..." which means he already got the girl, so what is his goal now? If that is his goal, then the inciting incidnet is falling for her in the first place, not winning her over.