Need help with motion settings

I recently purchased 2 battery security camera. 1 for the garage and 1 to overlook the font door. The garage one is working as we expect it to but the one over the front door is going off all the time for seemingly no reason. I have it set for people only mode but it won't always even pick up people. An example would be I went out today to get the mail and it picked me up coming back into the house but a few hours later a delivery person dropped off a package and nothing. It did not even register there was movement. I get notifications that there is movement when there is nothing there. There is a tree close by and I have a flag that is in its view but I would expect with people only mode turned on it should only pick up people and not flags or trees.The motion settings for the front are motion verification is on. Motion Frequency is standard, and the sensitivity is about 3/4 of the way to max. I am really not sure what to do or what setting I need to turn on to get that camera to pick up all people movement. Any help or advice would be greatly appreciated.