Objects Welding

Weld is unfortunately not always perfect so these things can happen.
In this case though, it looks like the "holes" are still there but you cannot see them and it may be because the subcurves are running in the wrong direction.

Select the object and switch to Shape tool.
Select a node on one of the subcurves and then click the "Reverse direction" button in Property Bar.

(You can also select the object, open the Fill dialog (Shift+F11) and uncheck "Fill winding".
This will not change the curve direction but will make Draw use another "fill rule" on the object, which makes curve directions unimportant.)

Yep, this happens to me often as well; especially when I convert text to outlines and then try to change it.

I usually view it in wireframe mode and delete the extra bits or change the fills to none. Of course this takes a few extra minutes... I can see the nodes in your screenshot so no doubt your outlines are all still where they need to be. Another way would be is to reflect the parts that worked and delete the ones that failed after your align them.

Safia

safia said:

especially when I convert text to outlines

This is because objects converted from text by default is set to use the non-zero winding rule where curve directions are important.
Ordinary curve objects use the odd-even fill rule, where the curve direction is unimportant.

As I said, there are two ways to fix the problem with filled holes, either correct the curve directions or change the fill rule to odd-even by unchecking "Fill winding".