Silly me....

I had a crazy experience today when buying landscaping grit at a place that sells it by the bag. You place your order, drive into the yard with the bags they provide, and someone comes and fills the bags and puts them in your car. As my 2020 Prime was being loaded, I started wondering if there was too much weight on the battery compartment. There were five bags, each quite heavy, but must be less than 400 lbs in total.
As I drove away, there was an alarm and a warning picture of the car showing the area by the back hatch lit up. Had I damaged the battery compartment afterall?
I panicked and pulled to the side of the road and grabbed for the manual. I could not find info other than that it would be dangerous to drive if the kind of warning I was getting was alerting me.
Finding nothing else useful, I rearranged the bags and closed the hatch again. Same problem. I placed two of the bags in the rear seat and one in the front passenger seat. This still did not fix the problem.
I finally decided to try Toyota Care. That was annoying and so I dropped out of the call and decided to call the dealer - but just before dialing went back to examine the hatch area.
There the problem was - a piece of the tarp I had spread out to protect the car was overlapping into the latch area - and the car interpreted this as an open hatch, even when the hatch was fully closed.
Looking at the warning light now, I can see that it is easy to interpret as an open hatch, but not if the hatch is fully closed and your brain is pondering damage to the battery compartment exactly when the alarm is triggered.