I want short text boxes that have been shrunk to sit side by side, but some won't

You need to consider the width of the shrunk fields as well as the width of the form. I would suggest checking first the width of the field.

Your last form ID is this https://www.jotform.com/90044506386355. What are the fields that you'd like to shrink here? Let us know, and well check.

Guide: https://www.jotform.com/help/328-How-to-Position-Fields-in-JotForm.