If a contact appears on page 1 of the contacts view, it cannot be merged with a contact on any other page. This is because when you flip the page to the next batch of contacts, the selection is lost. That means that you can only merge contacts that are within range of about 50 contacts of one another. What a silly loss of functionality.
Thanks for the feedback! I’ll pass this along to our team for review. We really appreciate you taking the time to share your thoughts.