Haven't really had the time to respond to this one, as it's certainly an odd set of auctions.
As you mention, those B slit/side sheets are very common for Series 12. (A side is tough, though). So a high price is strange.
My initial thought was maybe the winner of the first sheet didn't expect their max bid to actually be called by anyone, and they'd win it at the usual price level. But they got burned.
And then when the second sheet showed up, they were pissed they paid so much for theirs, they just wanted to bid the auction up out of spite just to make the next person also pay a high price.
I'm sure the Germans have a great word for that.
But with all that extra info you dug up, bidding order, etc., looks like there's more going on, as you say.