While I appreciate the message you are ultimately trying to communicate:
When running a large track (common rule of them is over 10 meters/30 feet) or when using more than 3 cars you should use two power supplies
and I also appreciate that it may have been frustrating figuring this out: To be honest you describing in full detail the behavior of ARC PRO when there is insufficient power power will surely help new users but I get the feeling you are trying to state there is a design flaw or something fundamentally wrong with ARC PRO that I would argue is not the case.
All powerbases produced that can drive more than 4 cars have 2 power inputs for a reason: You need extra power.
Also ANY layout, either analog or digital over 10 meters might have problems, particularly if the connections are nor perfect.
Finally, this very question has been asked on here (and other forums) many many times and answered, usually within a matter of hours.
I only have the ARC PRO upgrade powerbase and I admit the quick start guide does not mention when 2 power supplies are needed but the very first picture shows 2 being plugged in.
Slot racing's learning curve is unfortunately a bit steep, digital in particular. It is not helped that there are no standards for digital either. Still, once this curve is surmounted there are very few things that could be arduous to resolve.
Let me reiterate: Thanks to the pain you went through many will now know what happens when the track is underpowered. This is something that I have never done because I have always known that when either 4 or more cars are racing or if the track is over 10 meters you need 2 power supplies.
I would like to encourage people though to use the search function or ask questions before wording things in an accusatory to inflammatory manner.
If that was not your intent I apologize but as I am likely thousands of miles away from you I can't hear the inflection of your voice or see your body language to know your intentions are purely benevolent.
I am glad you got it sorted out, I have raced on a 20 meter track with 6 cars for 10 hours straight without problems (with 2 power supplies!) so I am sure things will work swimmingly now.
Enjoy the holiday weekend if you can!