The relation drow down (select2) currently contains about 5 items. In some situations this is a low number, for example when many images have the same title.
Increase the number of items to 100. The select2 box should already support this. (if not we need to re-refine this issue)
Current JSON URL: /admin/content/?relation=media&limit=5&sort=title&_format=json&q=titl*
New JSON URL: /admin/content/?relation=media&limit=100&sort=title&_format=json&q=titl*