I just purchased the 21" push mower a week ago and used it twice. I noticed a constant rattle sound during mowing and found it to be the battery cover. When latched, it has about 1/8" vertical movement and 1/16" side to side. The unit was built 4/17. I am surprised the cover doesn't latch firmly in place since the unit will vibrate by nature from the spinning blade, traveling across a lawn, etc. The rattle is actually louder than the motor/blade spinning. Does anyone else have this issue?