Short description of error
Labels in the dropdown box are mixed up with other elements of the tuple list (like ID), but only if you use the expand=True view.
Exact steps for others to reproduce the error
This bug is related to the already closed bugreport T50426.
I made a script where a curve can be labeled to be put in a an EnumProperty. The curve has a collection of some random numbers in a CollectionProperty. When an empty is selected a panel will appear showing the EnumProperty containing all the labeled curves and a EnumProperty containing the random values belonging to that curve. Each time you select another curve, this list needs to be updated also. The EnumProperty with the random numbers shows fine in a drop down box, but when I create buttons of it, with the option expand=True, the labels are all mixed up (see attached blender file).
I hope I don't do anything wrong and do not bother you with stupid bugreports !!