By chance (pure guess) could it be that one of the items has a bunch of spaces at the end? Are you Trim(ming) the values before adding them to the combo box? Have you used Length to see what the longest length item is that is added to the combo box? Just noting some things that could be investigated...
No, I have not checked, the data come from an example db found on internet, but I think there are no spaces at the end. If I haven't already thrown it all away ? , I can check it anyway.
On the other hand, the purpose of my version, a modification of Erel's B4XComboBox, is for the classic list of texts of a field and their IDs; it would be sufficient to truncate the texts, all with a maximum length, since the important data to be obtained is precisely the ID.