Not being able to stack two individual pieces of fabric is very annoying and would be great if there was a fix.
This might also apply to other items too as well. As long as you have two of an item you can stack it onto other single items with shift-click.
Also if I have two single items that cannot be stacked and want to add to a recipe it won't let me since they are not in a stack, because I assume when I try to add it to the recipe it is just swapping out for the other. This to me, is the big problem because I'm not able to make the item then.