These are all good questions. Isn't populate a separate download? The textures or something? Maybe you just need to install those if some function is trying to peek at populate data and it doesn't exist. That would be nice if it was that easy to fix. If it's a corrupted windows user, that's a bummer. But it might not be, it might just be a case of something looking for some of those textures from Populate and not finding them.
Maybe the design toolbox is a script from a while back that gets copied into new max installations but is no longer stable. I know I'm guilty of copy/pasting my plugins folders onto a new version. Otherwise, does it sound like something you can live without? (Doesn't select and place kind of do a lot of this now?) I didn't watch the full video so I could be off there. But an old function on a old script can wreak all kinds of havoc on occasion.
As far as corrupted user, that's an interesting case. (I assume you mean windows user profile and not 3dsmax user data. I haven't had a corrupted 3dsmax config file in a very long time, since 2018 or so.) My guess is that if a Windows machine is powered off without using the windows interface then perhaps it doesn't properly write to a config or data file that it would normally, and things get out of whack from there. Someone in that link suggested something similar and given your expertise it's got to be related to either that or power. (Also, not using things like CCleaner which seem good but over time mess things up.)
Now I think we both know the life of a render artist is such that "whoops, I accidentally set the light cache samples too high and now my machine is locked up, better rerestart manually" is a thing. (or maybe it was subdivs, bad forest pack density settings, too low a noise threshold on a bucket render, you know the game.) Maybe doing a hard reboot like this often enough will corrupt the profile over time. I can't say for sure, but as a former full time render guy like yourself, that was common scenario for me and I have had my windows profile corrupt about 10 or so times in my life. (4 were from Avast, never again.)
There is a relatively easy workaround though. We both know how long it takes to install all software, plugins, activations, etc. It takes forever on a new machine. If you use something like Macrium reflect, once you get everything perfect you can image your machine back to the latest stable working state on a whim. If you have a separate drive for project files and install your programs on your fast SSD drive (C:), then it's pretty easy to get back into the game from your last image. I do a macrium backup once a month. Only downside is having to redownload all my emails again and that they are marked as unread on my local email client.
Best Regards,
