Hi Kenneth,
There are a few possible reasons… Normally, it’s because some of the clicks are not waiting for the main page to load. It can happen if the traffic source is inspecting your links with their bots or if the link is taking too long to load for the users.
I suggest that you check loading time (if you use a proxy or VPN, bare in mind that it will naturally be 30% – 50% slower than with a regular connection) and see if all the clicks are counting as link clicks on your traffic source (if not, it can confirm that it’s their bots/crawlers).
William