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Simutrans-Extended development / Re: [6.6] Mess with the distance_per_tile again (or still ?)
I actually can see this "second factor" for maintenance. Well... even 10 of them

Sure, they are derived from main distance_per_tile, but they are separate variables.
And actually this gives the last piece of the puzzle to us !
We know the identity of MBMM. All those cst_* variables are together MBMM.
If you load pre-6.0 save, because of the bug, the maintenance is scaled by CDPT, while later OSF is read as DPT for savegame.
Thus, this gives results exactly consistent with my theory !
Yay !
Now I'll have to start thinking on the hard part of the problem. How to explain even more crazy behavior of my old, old savegame. It was originally created in Simutrans-Standard and then migrated through several older versions of Experimental (2.x through 3.14). The funny thing it behaves differently than plain 3.14 savegame.
But at least the first part is solved !
[Edit:] Actually, after looking at the posted code again, I see some things that might just be responsible for the old old savegame behavior. Would have to think about that though.