here's my guess.


brake dust and dirt builds up in the pistons and when you pushed them back in, the o rings are now rolling the pistons back in the bore when you let off the brakes. it doesn't take much.


buy some brake grease. its this clear shit that doesn't eat the rubber o-rings. most auto part stores sell it for cheap. pull the caliper off, pump the level to push the pistons out. clean them up with brake clean and then lube them up and push them back in.

do that to all of them, bleed normally and you should be straight.