Don’t worry about it - that’s normal to see the aluminum showing either at the top or the bottom. Tighten the net well and it will hold all in place. Bang it the hoop with the palm of your hand once or twice without going crazy, then tighten the net or tighten the net first and hit the hoops next. Either way it will do the job. Relax the net all the way before inserting the battery or it will catch the two upper corners of the container. Then, tighten the net to hold the hoop in place. Relax the net again when removing the battery. And with use of your machine over time, all will loosen and be easier to install.
More important is to keep an eye for any play at the connection of the side bars to the frame. The washers will compress a bit. Using blue Loctite will help. The connections should snug - not to tight so to impede smooth rotation at the joints. Checking for any lateral play should be part of each pre-flight check.