I put the front bracket into Tinkercad and designed some little "feet" to act as locks. This prevents the two side/vertical panels from splaying.
Here's the tinkercad edit: https://www.tinkercad.com/things/2hguPt8Ebnj
The orange face bracket in the pictures is the original; the replacement/remixed version is the grey one. I modified it further and attached the STL to this thing, it's a lot easier to print with flat locks than the projecting locks in my grey version.