BirdieSync

I am trying to evaluate BirdieSync which looks promising. Installed the app on the iPhone, installed the app on the PC and in Thunderbird... trying to sync the calendar. The PC can talk to the iPhone and pushes events to the iPhone, then tries to de-duplicate. It complains about a couple of events that it cannot "resolve" then reports an "unexpected error" and stops. The PC considers that the sync never took place (still reports the iPhone as unsynchronized) although there are some events on the iPhone. In fact, plenty of duplicate events since it keeps recreating them everytime I run the sync, and fails to suppress the duplicates.

Is there anything I'm doing wrong? At that point all I can say is... would be nice if it worked, but it does not ;-(

For what it's worth... I have created a new calendar in Thunderbird and moved the tasks in that calendar, and then configure it so it is not synchronized. With that setup, all other calendars synchronize fine and I've been able to cleanup the du- (or tri- or quad-) plicates that BirdieSync had created.
So it looks like things are back on track... but before finalizing my purchase I'd like to hear from BirdieSync about that situation... is it expected? Anything I should do to avoid it? Can I help troubleshooting?

Quick update: I did get in touch with BirdieSync via the chat and got awesome support. The issue seems to be caused by some tasks in the calendar (which should not be synced anyway...). They're currently investigating what's wrong. Pleased with the very quick response.