Creating DDP crashes when "Mix to Mono" set in master

Creating various masters that are stereo montage, but the audio is mono. I always “Mix to Mono” in the master section, but now Wavelab 9 on my Windows 10 pro crashes when trying to create DDP. I have been doing this for decades, but now it is not working. Anyone else have this happen? Is it possible there was a Windows update that is causing conflict?

I am not sure of your exact configuration.
If the output setting of the montage is Stereo, you should not need to use “Mix to Mono”.

When working with pre stereo reissue material, we often use Cube-Tec VPI, or Cedar restoration tools. Much of this work is disc based transferred with a stereo cartridge. It is “Mixed to Mono” with azimuth alignment tool. This is done in the mastering section.
Also, said restoration tools sometimes create a phased artifact that can be negated when “Mix to Mono” is used in the master section when creating final master delivery formats.

Try this: open the Stereo Enhancer plugin, and set it to 0%, to convert to mono. Does that solve your problem?

I reopened this montage on other systems and it had the same problem. Then I tried another montage and there was no problem, so it seems the montage was corrupt somehow.
I would not have been able to use the Stereo Enhancer plugin as that would negate my Azimuth correction VPI plug in from Cube-tec.
Thank you.