Why is my column sort not applying to all items in my Microsoft List?

Question

Hi, I can't work this one out. I have a Microsoft List that has 15 columns. One of the columns is "Candidate Name" and is a single line of text field. There are around 200 items currently and when I try sort alphabetically by "Candidate Name", it is only sorting the first 62 items A-Z, and then going back to A for the remaining items. It's like it's treating them as 2 separate groups. There are no other sorts or grouping this list and there is no rhyme or reason as to what group each item falls into - it's sporadic. Any ideas?? Thanks!