I've written a formula that filters out projects from an overall project list if they appear in a SharePoint timesheet list.
Filter(ProjectList, Not(Projects in 'Timesheet Lines'.Project))
Strangely using this formula in the Items property of a preview dropdown doesn't display the correct text values, but a mysterious sequence of numbers. Referencing the selected value of the dropdown (drp_NewlineProject.Selected.Projects) returns the correct value though. The classic dropdown doesn't have this issue.
Here is a screen shot of the buggy preview dropdown (selected) and the classic correct one on the right.

Has anyone else seen this issue?