Hi
Have you considered looking at the usb stick with a disk hex editor. Like can you read the data over the full capacity of the drive? If so can you change the data and save it back. There maybe some areas like the first 100 mb with the promotion stuff which is not even flash memory, perhaps write once memory . If so then you can partition the drive after this area and format it for use.
Hex editor link
https://mh-nexus.de/en/hxd/I haven't used it in years as Paragon Disk manager which i use has a hex editor.
Something else i have noted when a pen drive fails this 8mb total capacity is quite common. I wonder if the controller chip has 8mb of cache which is what you are seeing.