Hi,
Sorry for the issues you are having. I can help troubleshoot this with you.
We were not able to replicate a duplicating of the events in the future as you are having (it was only recently past events) and not seen other reports of it so not sure what is the cause on your site.
I have tried to replicate the problem using the same settings and Facebook Pages from your site and was unable to.
For all the duplicates I do not see their Facebook Page in the Automatic Import List from your system settings you included, are those being manually imported? Or did you remove them?
Let me know and we can go from here.
Thanks