I tried to reproduce the same issue locally, but to no avail. As I tested the described problem I did not find any problematic visual elements on the Document Manager in RadEditor. I am attaching a short clip showing the test process, so you can let me now if I am missing something that leads to the scenario in the attached picture.
As I am just guessing about the steps leading to this issue I would recommend you to check for some custom CSS rules in your project that can lead to such problem.
After reviewing your project and you still encounter the same issue, please get back to me with a sample project that isolates the problematic scenario, so I can investigate the visual problems.
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