Lightning usage in Dropbox with external calendar bugs

Lightning makes trouble when used with Dropbox.

I have installed Lightning in the Portable Thunderbird. That worked!

But I wanted to share my calendar with someone so I put in on my dropbox and shared it with that person. That was leading to conflicts... damn

Now I tried another way. I copied the whole folder. Everyone was now using his own files. But here we also getting conflicts...

By the way the calendars are just linked and we are working on the same files. And somehow also if you are using it alone (I mean the calendars) you sometimes getting conflicts (well at least I think I was using it alone...I was not able to make this sure).

So my question, am I alone with this issue? Did someone else tried to share a calendar in Dropbox? Is this maybe a Dropbox issue?

Thanks for any ideas/feedback.