Facebook Lead Gen Ads - Issue with lead counts not matching

Hi everyone,

We are seeing an issue with our Facebook Lead Gen ads where the number of leads that I see in Facebook is not matching the number of leads in Marketo. When comparing the two lists, I noticed that there are 4 people in Marketo that came in from that specific lead gen ad but are not in the list that Facebook generates. Likewise, there are 6 people that are on Facebook's list but are not anywhere in Marketo? This ad ended several weeks ago so I know its not an issue of the integration running slowly etc. I dug a little deeper into the people that I can see in Marketo (but aren't in Facebook's list) and they do fit the audience that we are targeting for this specific ad. I can even see in their activity history where the new person was created by Web Service API via Facebook Lead Gen Ads through the specific form name (FT20_PC1087) but again, this person is no where to be found in Facebook's list. 

I was wondering if anyone had ever encountered this? I did submit a ticket to Support but was just told to contact Facebook. 

Any thoughts or ideas would be helpful!

-Tegan