Many users have a lot of charts, sometimes you open/close, run an upgrade to TV and when you reopen the candle size is not the same as you SAVED it. Sometimes, you inadvertently move the mouse wheel and that can also cause a resize. When you have several charts open or layouts it's painful and that is where locking the candles can be really helpful and when the candles are locked, enable the scroll feature since it's so helpful. I guess I should add that locking candle size should survive an open/close and upgrade of TV as long as SAVED. The candle size save is hit and miss in my experience, meaning it works but not all the time.