Friend Folders

Sometimes my League friend folder magically change the order I put them in.I prefer to put the people I usually play with on the top,and sometimes it goes ALL THE WAY TO THE BOTTOM.Then i have to manually move it make to it's original order.It gets really annoying because i have around 9-12 friend folders.Is this some bug?This usually happens when I log off,then log back on the next day or few hours.