I found a problem working on a small scene with few rectangle lights. Corona ver. 1.3 official relese.
The problem occour when you create the light/modified it and after that the light disappear. I found short solution as selectin the light trough Select by name option.
I uploaded a gif file with the problem.
Try to change max drivers (Nitrous, directX wtc..) and see what happens.
I thought we were done with this issue long time ago witn new drivers and max versions. I had such kind of problems few years before with old versions of max.
Now after swtiching viewport drivers the prolem disappear but i lost all AA filtering and everything is jagged… anyway - thank you @cecofuli
Maybe because I’m an old school, but I don’t like AA viewport in 3ds max =)
cannot reproduce, probably fixed because we switched light drawing to nitrous