There is another aspect that comes with the assumed tête-bêche lay-out.
A few plate characteristics occur in two versions! Some with an extra characteristic in the stamp elsewhere but only depending on the direction of printing i.e. which pane of the double-pane lay-out!
My conclusion so far is that the multipositive film comprises 10x10 stamp images of which a few have these characteristics already! The additional characteristics are either on the top or on the bottom pane..... The multipositive characteristics - NO plate flaws! - are to be found with stamps on uncoated paper AND on stamps on coated paper [either with L or R] whereas other charactersitcs - probably real plate flaws only occur on uncoated paper! The "tuba" does not occur on coated paper!
to be continued ....