I strongly advise against customizing the
X-UA-Compatible meta tag.
You should use whatever is the default for that version of SharePoint (default master page) for maximum compatibility.
After making sure your master page is fully checked in, published and approved, close the browser completely (otherwise you will be stuck on manually changed modes) and test it.
Based on your IE Mode and IE Browser version, if there are still issues, you may have to add additional CSS.
For example, rounded corners and SVGs are not supported in IE8 mode (used in SharePoint 2010).
If you want to use the meta tag regardless, use a SINGLE instance (not multiple tags, not semicolon separated values) and set it to
IE=EDGE, but don't be surprised if some functionality that is specific of Internet Explorer no longer works.
If you can fix the problem without messing around with the meta tag, that would be preferable.