Could the tie rod end be totally dry of lubricant? Perhaps under presure it moves suddenly as the rust releases under pressure. (your pop) Still would not be really worn but the iron oxide( rust particals) will eat up the joint even with the addition of new lubricant. Plus the nice smooth surface of the joint inside would be gone.If the joint seems still quite tight that is probably the reason. Yes it should be changed. You can remove the rubber boot after removing the tie rod end to satisfy your curiosity. Just reread your post and sounds more like a worn out joint or the pocket has been stretched more so than a partially seized joint. Good thing you noticed it and checked it out as a lot of people may have driven on it till total failure.