Update on daughter's PE:
Took the cover off, and checked that all cable connections were secure. When I messed with the one in the picture below, the device booted! The photo shows the connection/cable. Notice the wires sticking out of the top and the misaligned black taping. Can we say sloppy assembly?
Rebooted it twice with everything taken apart, then started putting it back together. When I snapped the cover back on to that side of the PE, it no longer booted. I took the cover back off and it did not boot. I plugged the power in to ensure it wasn't a dead/low battery causing the problem, and immediately smoke started coming from the area of the cable.
There are burn marks on the underside of the cable.
So - I am in the process of moving the cable from the broken screen PE to my daughter's PE, instead of moving my daughter's screen to the previously broken PE. This new endeavor involves taking apart the hinge. . . fingers crossed. . .