Answer:
A weld must be connected to two elements at its two edges. Otherwise, the message shown in Image 01 appears.
Element 1, Element 3, and Element 5 are connected at the edges (marked in red) of the weld shown in Image 02. Therefore, the message shown in Image 01 is displayed.
It is necessary to modify the cross-section so that two elements are connected to the weld (Image 03). This is also shown in the video.
