The two black pulleys are the stock plastic ones. The silver one looks like an aluminum aftermarket pulley. There is supposed to be a type of pulley mount, or "raised" washer, that the bolt buttons up to in the stock application. The bolt, when torqued down, applies pressure on the steel washer, rather than the bearing itself, so the pulley can spin freely. I don't know the actual name of this part. But I don't see it in your photo, and missing that washer could cause the problem your describing. I have the steel idler pulley set from SCP and it has worked fine for years.