I recently watched the re-mastered, extended HD edition. It's the 3rd film in the Argento "animal trilogy" from 1971.

It's a thriller about a guy in a band who notices he's being followed. Upon confronting the stalker, he apparently stabs him with a knife by accident, but someone else photographs it and uses the pictures to harass/blackmail him.

It didn't really have the same problems as Bird With The Crystal Plumage in that it was very patchy, instead, it was the opposite; it was just very flat. It had more arty shots, which worked quite well in the context of the film, but the humour (the gay characters especially) didn't really work at all. I didn't really get on with it as well as Bird... but glad I watched it. It was alright. There were massive plot holes and I knew who the killer was from the first moment they appeared on screen. Thought that the main bloke was an idiot for not seeing it at all, so the reveal was just plain shit. The motive was ridiculous too. But it's just so damned entertaining!