This is not unusual and sadly more common than people realize. I like to call it a sort of click fraud.
You mention its not about ads so its important to note are the links clicked truly viewed by user links or links multi scrolls down? Make sure you tag each CTA relevantly to allow you to differentiate referrer source even if its not an ad. Can be tough if it is a shared organic link I know
Also you can do a deeper dive analysis like I have done I will tell you my process and what I found:
If we are to rule out that browsers block/drop tagging code so we are in essence missing some of the users from the Analytics side we need to go low level. You will need access to your main webservers logs. These logs look at whats called GET requests, these request will show the actual referral URL(so anyone from Facebook). Whats great about this is that you can isolate by IP address/link and useragent.
Bottom line I looked at individual complete days 1 at a time. I isolated all facebook requests and even a specific page where my ad was targetting. I then matched them to IPs and I looked at actual date stamps.
Off the top I noticed my numbers were pretty close to my analytics numbers maybe a few % higher as some users indeed seems like analytics didn't have time to fire but I saw they came to website and based on timestamps was for milliseconds.
I then started to notice some odd patterns. So clicks were not coming as randomly as I would expect in fact most came in bunches. I would have thought every few seconds or minutes we see a new IP hit but I would see anywhere from 3 to 8 all within the same sec(just a few milliseconds difference). What also boggled my mind was some of these FB referrers accessed 3 different referrer links on the same page within a few milliseconds of each other. It looks like we have super fast users clicking 3 links in under 300 millisends.(A bit sarcasm here dare you to try and click that fast)
Bottom line seems there is a lot of bot like traffic and bunched traffic getting send from many of the display services. If the traffic I measured on my server side was this suspect imagine what traffic tricks the Ad displayer could be doing.
Something I have found to be really useful and allows me to strip out alot of the bot like traffic if you are using ads is just simply use floodlight pixels from FB or Google. Then make sure you create a 1 or 2 sec delay before the pixel fires.(so allow a real person to have the page load have a bit to actually see your page content).
Once I started doing this I suddenly saw my ad conversion rates more closely mirror what my analytics all along was showing.
Hope this helps you!
Pablo
