I currently have the issue where if I’m driving for more than a half hour or so my brakes start sticking and gets to the point where my brake pedal goes rock solid I’ve just changed the callipers thinking it was them but have the same problem , also if I’m coming to a stop and I am pressing the brakes gently the brake pedal sort of vibrates and jumps up and down a bit bit stuck on ideas as what it could be so anyone have any idea what is wrong is it something to do with the master cylinder or brake booster if it starts sticking and the pedal goes hard and I turn the car off and back on while holding the brake the pedal frees up and isn’t rock solid anymore
thanks

 

Sounds like the anti lock motors , but I'm no expert on those . Try one from a salvage yard , you'll need to learn a good bleeding system so try bleeding them first , maybe one hose is collapsed internally .