2013 Ddge Jrny shutters bad if brakes applied after a long steep downgrade?

What is your question?

Only after long steep downgrades when you apply the brakes the whole car really shutters and feels very unsafe. It does not do this when applying the breaks on inclines, flat ground or short downgrades. Any idea what is wrong? What seems to make the problem better or worse? bad vibration only when braking on steep downgrades How long have you had this problem? years