I created a bracket that is 3 mm thick and when I merged the 5 objects, everything was fine.
While I was printing the bracket I noticed that 3 mm in aluminum feels pretty solid, but the PLA test didn’t look so solid at 3 mm. I used the original sketches and created a 6 mm version, but now I can’t seem to combine the objects anymore without strange tesselation; if that’s even the right terminology for the problem.