Lightmix setup sometimes 'locks' 3dsmax interface

[OccultMonk]

When I press setup Lightmix and then Generate, 3dsmax randomly sometimes 'locks'. I get a windows 'ding' sound, as if there is a modal dialog hidden somehere. I am using 3dsmax 2018.2.

[TomG]

Would need some more info, as I've never seen this happen:

Does this happen in every scene? Or only in particular ones? For the scenes it happens in, does it always happen with that scene (or can you close Max, restart it, load the same scene, and this time it works)? Can you share a scene where this has happened at least once? What options do you have checked in the LightMix dialog (a screengrab would do nicely there). Which version of Max and Corona? Cheers!