OK. I have tried nearly everything recommended on this site and on xda-developers to fix this boot loop issue, and nothing works. This is a standard unlocked GT-P5100 running 4.0.3. It was running fine and then one day it started to boot loop. It was never used much, and it basically spasmed sometime around a year ago. I have tried:
Deleting cache and factory reset from various mechanisms. They generally say that they work, but don't actually delete anything.
Using ODIN to install TWRP said it had succeeded, but nothing actually changed.
Using ODIN to install CWM said it had succeeded, but nothing actually changed.
I tried various rooters, Kingoroot being the last. It said it had worked, but I see no evidence of that . I successfully (apparently) rooted it via ODIN, but again, there's no evidence of that.
Flashing a new version with ODIN gives me the message: "Complete(Write) operation failed. All threads completed. (succeed 0 / failed 1)"
I tried to re-flash the same version but nothing changed. I managed to get an actual upgrade to a later version of Android flashed once, according to ODIN, but when I checked I was still on 4.0.3.
Some issues that make it more difficult:
The re-boot cycle can be as short as 10 seconds, so I often have no time to do much. In upload mode it seems to last for as like as I like.
Changes I make don't stick. I can set the USB debugging switch on, but after the next re-boot it's gone. I have tried deleting apps, e.g. Chrome, to free up space, I shouldn't need to, of course, as I have about 8Gb free. I never succeed in deleting anything, although I get an Application Deleted message, and then an immediate re-boot.
So it looks to me as though something is smelly in my RAM.
There is nothing I need to keep, my wife just uses the toy to google the news while we are travelling, so if there's anything radidal I can do, by, for example running something brutal from the SD card, I would be happy to do it.
So. Any ideas, please?