Hello Guido!

The devs completed their investigation, and it looks like one specific item is causing the synchronization issue...

Could you please:
* Remove the account logger you created.
* Add a new account logger using the same arguments as the old one and adding "window_size 1" at the end of the command.
* Force a resync of the contacts on the phone.
* Wait until no more contacts are synchronized and send the logfile to community@zextras.com.

This will help us identifying the troublesome item in order to understand what's ultimately causing the issue.

Have a nice day,
the ZeXtras Team