Bending Mobile Goal Lift

My teams mobile goal lift tends to bend in when it has a mobile goal on it. Is there any way we can fix this? I have included a picture below as an example.
finished mobile goal lift.jpg

Slop in the joints, This can be helped by using screw joints with bearings instead of axles. May also be partly due to the joint (edit: i am referring to the hinge) used to support the tray allowing it to flex.

In this case, a triangle support setup like the image below can help.
You can do the support on the front or on the back.

Thanks! We will implement this and see how it does.

Use a one-by and attach it to each corner and attach the other end. It is strong enough because it’s a triangle.

this is what I would use a mobile goal lift. Also if you have alumminum parts I would use that too.