My son will not stop hurting people

He's almost 5. He's bit a few kids at daycare. He pinches his younger sister everyday. We've consulted psychologist and implemented their suggestions and nothing changes. Timeouts don't work. Taking away his stuffed animal doesn't work. We have consistently tried different techniques for many months at a time without change in behavior. About half the time he uses these skills we've taught him (identifying his feelings and expressing them nonviolently, coming to get us, etc.), the rest the time he pinches. At least he's not biting or hitting consistently anymore.

Maybe I'm just venting, or maybe someone has advice?