Second this. If it’s PLA, improving layer cooling might help stiffen the last layer before the next is applied. If it’s not PLA, slowing the print down can reduce the horizontal forces for slower-cooling filaments like PETG/ABS. If there’s any warping or over extrusion leaving little blobs on the surface, your nozzle can bump into them, breaking cantilevered features like this one, or breaking the part off the build plate. Getting retraction to blob less or making sure no over-extrusion exists could help. If it’s PETG or Nylon, printing slightly wet (where the surface doesn’t look bad) can cause blobs on the top layer that the nozzle hits and causes those horizonal forces.

Prints like this aren’t impossible. I’ve printed a PETG storm drain that had vertical slots like this when I couldn’t buy one I needed. It turned out great but I had to print really slow.