Good day. You stated the brakes pull to the right sometimes and to the left sometimes. Does it pull one way with the pedal pressure on and the other with the pressure off? I had a problem with my brakes, when I put my foot on the brake pedal it pulled left, when I took my foot off the pedal it pulled right. The flex hose on the right side was deteriorated, when the brakes were applied normal pressure got to the left but not to the right so it pulled left. When I took my foot off the pedal the left brake released all the pressure but the right didn't and dragged thus it pulled to the right. I replaced the flex hoses and the problem ceased. The hoses may fail internally and if a piece dislodges it can act like a check valve in the line but look good from the exterior. I'm not saying that's your problem but it's something to check if you run out of ideas.