Custom Clothes Export for Unity does not look right

Hello everyone. I hope someone has the answer to my problem :sweat_smile:.
So I created a custom cloth for a character in CC4. I modelled it in Blender and no artefacts were visible. In CC4 everything looked good, too. I attached a parent to the cloth and transferred skin weights, so it would move according to the body. When I export the character for Unity and import it there, the cloth underneath the armpits looks very wrong and has artefacts. But I do not know the cause and how I can fix it. Has anyone an idea of what that could be?

Here is CC4:
image

And here is Unity
image