maybe this is a known issue, but many of us here have noticed that in max 2018 corona will start rendering even if you are just entering a numerical and pressing enter (for example it just happened when entering the displacement px setting).
very annoying. dont know if its a max issue or a corona issue.
Same happened here. When I changed some values in the render setup and press enter, corona started to render.
I cant tell anymore if the regular enter button or the numpad version was used. But I always use the numpad to type numbers, so I guess I using this one.
But it’s gone for me. Could be that the latest 2018.3 Update fixed this. I will test it again