Has anyone else been experiencing this lately?
I have been running on FB for awhile using the pixel and FB has always shown the same number of conversions or less than the offer network. However over the past week FB has been consistently showing more conversions than the network. For example today FB shows 56 conversions and when I log into my affiliate network I only see 42 conversions.
I have accounted for timezone differences and just can't figure it out
This is very common when you are running something like lead gen.
Here's why.
User comes in, they click your lander, then fill the offer. and get to thank you page - pixel fires.
Then they get to the advertiser, they run bunch of automatic checks like valid # checker, valid address check, etc and it turns out, this lead has incorrectly entered something or another. They ping back the CPA network and say invalid lead.
Facebook fired the lead, the advertiser rejected it.
OR...
You're getting shaved. 
Thanks guys, this is for a nutra trial offer so it takes a valid credit card for the pixel to fire. Also the stats in my tracking system match the offer network as far as conversions.
I'll try switching the offer or network and see what happens
have you tried contacting your AM?
Are you using just one event? Multiple events show up under the same row.
Did they change anything like increase the payout?
Yea split test with another network, to rule out the old shave&scrub
Since you say it's only behaving like this for the past week or so, it's quite possible that there has been some change made to the flow and they messed up the postbacks and it's now also firing in case of some newsletter registration for example. I've seen this with a few PPS offers, they were sending me the postbacks even when someone registered for free, when I only wanted to get the full sales reported ... definitely ask your AM about this, they should be able to get the info for you.
Lol @ any network that shaves but lets your own conversion tracking JS/img still track the shaved conversions.