There are 2 issues in thunderbird on Sync adress book :
First, when we sync, there are empty cards
Second sometimes, somehow... the adress book is summing card on sync, and at a moment, there are thousand of card in adress book instead of hundred for example
I 've found something.
Apparently Thunderbird can't understand that property.
I've tried a fix : I add "PREF=1," before "INTERNET" on line 305 (CardDavDolibarr.php), and it solve both problem.
There are 2 issues in thunderbird on Sync adress book :