I like that it’s not a fully enclosed design, those always feel like they’re not making the best use of the printing process.
A fillet on each of the vertical edges should help with any warping on the main body. Adding a brim if you haven’t already will also help.




The triangles are a result of the print “wall” changing thickness. Look at the corner on the left. All 10 perimeter lines go all the way round. If 10 go in and 10 come out, we need extra perimeter lines in the corner to fill the extra width. That’s why there are triangles.
I imagine you could fix this by making the walls the same thickness at all points, but without trying I can’t be sure.