>>/6197/
So.
When the migration happened (when the bunker was online) Odili tried to restore the site as was, with thumbnails. The migration script run, then failed, so it had to be restarted. Turned out certain boards contained a couple of corrupted files which caused an error and stopped the script. So these boards got onto an ignore list for the script and every time the script had to be restarted, and when failed at another board, that board got on the list, then restart and again and again, this is why it took so long. This is how most boards got to their thumbnails back in the threads but not /rus/ and a couple of others.
Note: thumbnails in the OPs weren't restored, it had to be done manually (like I did on /kc/ and advised a few boards to do the same).
Despite this Odili said he could try to take out the old database and give it a try.
But it would be best to just delete the affected threads (so the old thread won't waste space) and reupload the content where possible.
Now that I'm thinking, maybe it's possible to run the script on per thread basis. The problem is not with the board, but some corrupted content, if those files could be avoided somehow, then at least some threads could be restored. Perhaps. Or perhaps now I write a fantasy.