I have Quad QHD-4 Axis Disc Brakes that were probably never maintained and are stuck. There was a lot of grime and dirt all over, the pads even rusted a bit. It probably locked due to this and I also pressed the lever after removal before I knew. For the life of me I cannot move one piston all the way in. I used a flat headed screwdriver and applied all my body weight to the screwdriver but still it would not move. Brakes are bled and completely taken apart except from the large torx screw. I even tried spraying WD-40 but it had no effect.
Is there anything else I can try? Would I be able to remove the pistons if I removed the large torx bolt? If so what bit is that? I cannot find any info on how to do this. It doesn't seem like the pistons can be removed without undoing the torx bolt and I think it would need to be cleaned well before use due to corrosion, dirt and WD-40.