I had a similar problem. Maybe my story can help. I had a very small leak on the slave cylinder. It was an odd leak in which fluid would leak out and then get sucked back in. Difficult to explain but the metal hose lines for the fluid was not tighten well, so the fluid will leak out and build up around the nut when I press the clutch down, when I let off the clutch it sucks it back in gradually sucking up air as well. Took me months to notice it.

So, suggest checking your lines and bleed them again, or double check the cluch pedal setting, maybe at the install they didn't adjust it to OEM spec.

Hope that helps,
Mike