I believe parts 26 and 14.2(in the image below) are equal parts, and they are different from part 14, right?
Sometimes the system doesn't recognize very well this numbering and can group members based only in the length, despite the parts are geometrically different, so, they should be treated as different parts with different item numbers.

Therefore, the correct item number should be something like:

To have this result, we can help the software to recognize which parts can be grouped with the same item number (equal parts).
In this case i would delete the member "14.2" and repeat the 26 using the tool REUSE:
REUSE will force to group equal members present in the model.
Here's an example:
CCarreiras