Finally discovered wtf is up with leather skill regressing - savegame at https://1fichier.com/?9qaust46tg1ing1f5no2
To triage I had to take the snapshot saves from my stupid script (btw, in the JScript version replace "getDay" with "getDate" - or don't) and since it was stupidly late in the evening I wrote a small abomination to binary search those, copying them to a scapegoat (save019.dod), running the merge, checking etc etc; the script is so butt ugly that if anybody asks it was actually written by a monkey pounding on a keyboard and it works by an amazing coincidence.
Good news is that this crap, even restarting MM8.exe whenever the script replaced save019.dod (it was too late to think of running the game in a window or whatever), took a more than reasonable amount of time:
$ time ./bsearch_mm678.pl timeline/save007.dod/*.dod
Now, if you're a computer person, one *could* reuse^Wabuse git-bisect (*) by basically writing a silly script that creates a dummy empty repo, adds all the snapshots as if they were single commits, and then... you got it.
When I thought of that I kept complaining aloud at how disgusting it is (I believe 763 is the relevant xkcd for this); if you're still reading, you must be Templayer, so please try the savegame, verify that the culprit is learning blasters in the control center under the oracle (and NOT in mm7), and do your magic with the info.
I ended up with those who had leather regressed to novice (same skill level, just no longer expert/master/gm) AND even dragons learning leather+blaster - except of course they can't use it, but they have the skill somehow.
Anyway imho the proper way to deal with this things is writing a tool that dumps human readable info to stdout, ie something eg like:
$ magic *.dod
save012.dod: Arius Axe 13 GM
I honestly thought I was going to rant for much, much longer, but I'll show some restraint(!) and stop here.
(*) or better, its fossil equivalent, since installing fossil, even on windows, is orders of magnitude easier than any other vcs I know:
1. download fossil.exe;
2. move it to a directory in %PATH% or even just in the merge/save directory;
3. you were done with step two!