Mid-airs unfortunately happen. Unless it is a blatant disregard for rules, it is very difficult to lay blame, However, that does not stop people from incorrectly doing so.

I had one not too long ago, both planes were flying in the same direction, they were in an outside corner, one plane was descending to turn on final and my student's pane was ascending in an attempt to clear the airspace for the other pane to land. they collided. I was barely able to save my students plane due to the tail feathers being broke off and only being held on by the control linkages, and a big dent in the wing LE, the other plane was destroyed.

Although I got the blame for the mid-air, the description of what happened given later at a club meeting was completely inaccurate, I decided just to blow it off and told my student not to worry about it because nobody did anything wrong.