So, this where the P08 BDM came in to it. Those details are here: viewtopic.php?f=42&t=6215&hilit=p08+bdm ... 00#p123110
All good I thought, I could erase, and write the flash without error. I failed to check exactly if the 0x4000 sector was recovered, because I could see the boot sector was all FF after the erase, and populated after the write. I naively assumed (dangerous!) that is was fully successful and moved on.
Today I hooked up the P08 ready to continue where I left off. Same problem - couldnt unlock. I looked at the debug console still 0x0000 seed, and still skipping the unlock. So I modified PCMHammer to not return if seed=0000 and set a custom key of 0000. Bingo! I was in. The screen shot above shows what was read. There were various retrying on the 0x4000 sector, obviously the chip was still not in a good state. And BDM was not going to get me out of this. I feared damage to the flash chip. So before giving up, I hooked up one of my commercial tools, and pcmhammer at the same time with 2 different interfaces. I put an hour long sleep in pcmhammer so it'd go silent after sending the key. I then let PCMHammer perform the unlock, and then started the write entire in the other tool. This worked! And running through a proper erase process got the flash chip back in to a healthy state. So now, time to break it with alpha quality code again lol. Hope this helps someone if they ever find themselves in a similar position.
(Im having a bit of fun here, no need to be serious).