I need a education on trailer brakes

[JMBT]

If the brake chambers are old they may be leaking internally. That can cause the brakes to be grabby by slowing release time of the chamber. You can take off the emergency line at one canister and have someone press and hold the brake pedal, put your finger over the hole on the chamber where you removed the emergency line and see if you feel air. Check each chamber the same way.