I also have this same issue, I was a junior member rank before I took a break from this forum due to some personal issues that won't allow me time to participate in discussion here.

Came back a few days ago to see I've been dropped back to newbie, I was skeptical initially but later on assumed it was due to my inactivity, was coming here to post a complaint but saw this thread already, and I am happy to learn that the drop in rank is due to lack of the required number or activity to climb and maintain the junior member rank, I will try to be more active henceforth to ensure this does not happen to me again.