Issue with video display on Safari (black lines despite border:none)

Hi everyone,

a similar question was posted on here, but nothing I have tried so far is working for me, so here is my issue:

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I have embedded a video on this page and customized the appearance with some custom code, including the following specifications:

iframe {
border: none !important;
border-radius: 1.5rem !important;
}

It works perfectly on Chrome and most other browsers and I don’t have any thin black lines showing up. This is a screenshot of when the video starts playing on Chrome:

However, on Safari, it looks like this (very clear thin black lines to the left and right of the video):

I am a bit lost at this point, it only happens on Safari and I have no idea how to fix it. I already set border: none for my iframe specifications. Can someone help me fix this display issue on Safari? If you need the rest of the custom code, I can post it as well.

Thanks in advance!