Set of Elements beign split in two

Hi,

Some sets of beams on my code are being split in two. For example, I have a given property assigned to a set of beams, and when I process the code or I close STAAD Pro, this set of beams becomes two sets of beams with that same property.

I guess it is a common and minor problem, so I hope I can get some feedback.

Thank you in advance for your help.

BR,

David