When you are welding objects with inside parts to another object, it is best to break it down to where you are just welding the outside profiles together. Meaning on the bottom design, first break the path, then select both the outside profile of the two parts you want to weld together and perform a Basic Weld. After the weld then you can select all and Make Path.
Note: Both objects need to be on the same layer, if you have multiple color pallettes on the right side of your screen (View > Pallettes > Job Pallettes), then you will need to make them the same layer. Select all or both objects and left click then right click on the layer color you want to use at the bottom of the screen (normally would be black).