The "Command" key on the Mac will give you the same functionality as the Control key on a PC. To keep your scroll bars visible, go to the System Preferences, General and select "Always" on the Show Scroll Bars setting.
I later found that when I plugged my phone into my computer, it became the F: drive. When I unplugged my phone and the F: drive was no longer there, the issue went away. There may have been a custom texture, material or referenced file that was on an F: drive on the originators computer that caused this message to appear on my system. The error message certainly isn't clear on what the issue is, but now at least, we have an idea on how to avoid it.
We received a totally different plan from another customer that was NOT having this issue, but it did happen to me, on my machine only. We were unable to reproduce it on any other computer. I was able to solve the problem by saving the plan with a new name in a new location. If you are still having the issue, try this step and see if it doesn't resolve it for you.
BTW, I was able to continue working with the plan... after clicking Cancel 36 times to that message!
We will continue to look into this issue to see if we can't find the underlying cause.
Here is a revised version of the update notes with a couple of additional items that were missed in the first version.
chief-architect-16.3.0.59-update-notes.pdf
It's been my experience that the Hotkey for this snap setting is usually the culprit. I generally remove the hotkey settings (or change assignments) for all of the snap properties as 0,4,5,6,7,8,9 seem to get accidentally hit too often!