Is it too easy to get demoted?

So basically, I'm a high plat Jungle main (Mostly Kha'zix and Diana) and I have been in my promos from plat 2 to plat 1, 7 whole times (Fun right) Lost the first 3 and then have won them ever since. The thing is, I have been demoted 5 times now from plat 1. The most recent one the worst, I go from 38 lp to plat 2 in 3 games. It just doesn't feel like your MMR is accurate when you win promos, I'm still just winning a few then get a small losing streak and go back.

So in conclusion. Is it too easy to get demoted as you get higher in a division?