Semi-successful story. PW3 shipped with the factory 5.8.10.1.
Trying to downgrade with the update_pw3_factory_5.8.9.0.1.bin failed as shown.

The usb storage was visible after reboot for 20 sec only. The official update file 5.8.11 was divided into four parts, each of them was copied to the device within 20 sec, then all parts were combined. The device updated, then one more reboot needed, finally the device started.
The problem is shown below:

There is a darker area at the bottom right corner of the screen, the same place which was corrupted as seen on the first picture. The device was updated to the latest official 5.9.2.0.1. The same screen with the darker area.
Any suggestion please?