miniPRO just died
 

Background: In 2017 I had a miniPRO that would not turn on after hitting a bump too hard. Segway tech sent to me some instructions on how to remove/charge/re-install the battery which solved the issue.

Here's the rest of the story:
In July my family and I decided to take a trip to Washington, DC and ride our miniPROs around the National Mall. I had noticed that this miniPRO (the one that I ride the most and it's the same one that had the issue before) was running out of battery power before the other 5 miniPROs when we would ride together. So, I decided that since they were all out of warranty I'd just swap the battery pack from one of the 5 that doesn't get rode much, and put it on my regular ride. This was done with NO problems and we enjoyed our ride around the National Mall with all of the batteries running down about the same.
After we returned from DC, I was in my home town, with the fully charged miniPRO, and had only ridden about 100 yards when I decided to cross the street. Halfway across the street my miniPRO beeped once, and shut off! Luckily, there were no cars coming and I was able to just step off and catch myself, pick up the miniPRO and walk to the side of the street. It would not turn on, so I carried it/wheeled it back to my car and went home.
When I got home, it still would not turn on so I followed the instructions from the email that Segway had sent to me beore in 2017 about how to remove/charge/re-install the battery and it worked!
I took it out the next day, around the neighborhood, and within 100 yards, it beeped twice, shut off and rolled to a stop.
I decided to swap out the lower circuit board, from the miniPRO that I had swapped the battery from in July and just use it for parts. I easily did so, and the miniPRO turned on and I rode it about 300 yards before it beeped and shut off again. Unfortunately, this time it would NOT turn on even after removing, charging and replacing the battery.
I ordered a complete base and circuit board from More 4 Mini and put it together today with much anticipation! Since this was basically a NEW miniPRO, except for the wheels and battery I expected it to work perfectly.
And it did... for just under 1/2 mile when it made NO sound but started leaning back as it shut off. It will not turn on. I have removed the battery and will try it again but I am nearing my wit's end.
Any suggestions?
Thanks in advance!