I am afraid that such an issue is not reproducible on my side with the latest version of UI for ASP.NET AJAX. You may check if the issue is reproducible on the RadMenu Render Modes demo
on your side with Lightweight or Classic render mode.
Judging from the screenshots provided, the menu on Mac Safari is not the same, which is tested on the Windows Safari, as it seems to use custom skin or custom styles, which may be causing the issue. Try to remove any custom styles and check if the issue is still reproducible. Note that there is no sample project attached to your posts, only screenshots.
And last, but not least, Windows Safari browser is obsolete and not supported by our controls. So any comparison with it is not relevant.
Telerik by Progress
Do you need help with upgrading your ASP.NET AJAX, WPF or WinForms projects? Check the Telerik API Analyzer
and share your thoughts.