Steps:

1. Create Content type with ezobjectrelationlist
2. Go to Content/Content structure and click Create
3. Select CT from step 1
4. Click Select content
5. Select some content items (it was 21 for me)
6. Click Confirmed items

Actual result:

Popup is partially hidden - see attachment please. User is unable to see all content items

Expected result:

Popup should expand also horizontally.