The described issue might be related to AJAX request where CSS resources of the Editor are not loaded properly. You can try if any of the suggestion in this forum thread
helps you to resolve the issue under Safari.
If you still have issues, please provide a sample markup demonstration of the RadEditor and RadGrid configuration to further investigate this locally.
On a side note, in this online demo
the RadEditor is used in Edit Template and I am unable to encounter the same behavior as the one described.
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