Google is always trying to improve Android and it really is getting better and better. So no wonder that when the new 5.1 Lollipop update came out everyone loved it, but there were some issues. On early versions of the build many forum users reported memory leak from the early Lollipop update. Instead of stability many users experienced crashes of apps and launcher issues.
This was all because of a memory leank, but we do not know when a next update will come out.