Shirt Texture Messed Up

Hi.
When you join two objects together, for their uv maps to join as well the names must match. So before you do that, rename a uv map to uv_0.
Also, unrelated, but before you start moving uv islands of the garment, you need to shrink them. Uvs generated in the square uv space of Marvelous designer stretch when rectangular TS4 textures are assigned, so you need to bring them back to the original size first with S Y 0.5 before moving.