I start new thread here to track this phenomenon.

I'm really p*ss*d off, because something is really wrong with that.
Luckily I make backup before playing around and based on my experience from
the past.

So here are my findings - no deeper code analyses yet.

When syncing 220 contacts to empty address book it ended up with only 72 in
the address book (vcf) configured.

This magic number 20 seem to be hardcoded undo steps. So what tdeabc was
doing, is saving couple of contacts and making backup and again and again.
Why the last copy of the vcf file had only 72 is still a mystery, but I
already had some headache with this phenomenon.

I think I'll have a closer look and play with it a bit. Perhaps I'll come up
with some improvement.
I hope I'll be able to reproduce this with the filesync or some test code.

Oh and BTW if one does copy-paste of contact from one address book into
another the encoding/conversion issue gets visible. I'll test the Fat-Zer
patch and get back reporting to the bug we opened.

I now understand what was wrong with opensync as well (haha - obviously
nothing) ... it took me just another 10y to come to the rootcause.

(to be continued)

regards