Which Umbraco version are you using?
V17.0.0
Bug summary
The Umbraco.MediaPicker3 shows the UI for multiple image selections when set to single mode.
Specifics
When "Pick multiple Images" is unset and the rest of the setting are like so:-
the UI looks like this:-
Note the extraneous "+ Choose" box.
Steps to reproduce
Add a Media Picker to a DocType. Do not set the "Pick Multiple Images" toggle. Create a new content item. Pick an image and note you still have the option to add another image.
Expected result / actual result
Expected to see one "+ Choose" box to select the first image and then nothing.
Actually saw a "+ Choose" box after the first image was selected.