I am having an issue in one of my Power Apps for Teams apps with the ComboBox.
On initially adding the ComboBox and configuring, it works correctly regardless if it's the FluentUI ComboBox or the Classic ComboBox. Once the app has been saved, closed and then re-opened, the ComboBox closes if you try to use the scroll bar or if you click on anything that is not a value. Turning Multi-Select on and off has no effect. There are no DefaultSelectedItems.
The strange part is it's only happening in this one app. I have an earlier app I created that works as expected with both styles of ComboBox.