Stats IQ: Inconsistent analysis results with pre-post

I am trying to run a paired difference analysis between some pre and post items. This is a matrix question with 6 different fields, and therefore I need to run 6 different analysis pairs (Ex. Relate Pre Q1_1 to Post Q1_1, Relate Pre Q1_2 to Post Q1_2, etc).

This seems to work for most of them, and I am getting language at the top saying "There is no statistical difference between." However, for one of the items, when I run the exact same analysis it does not provide any information on statistical significance. Instead it just says X "tends to be slightly larger than" Y. Any idea why running the same analysis on items from the same matrix could produce differing results like this?