Designs not available for certain jackets when combined

I’m having trouble with combining certain designs for use on jackets. Separately, both the designs work for all the kinds of jackets I want to use them on, but when I combine them into a multi-print-area design, only some jackets products are available. I’m struggling to understand why this is, and what the printing constraints of each product are. Any help would be greatly appreciated!

On most jackets you need a design in vector format for front print. Back print works with png also.