Browser issue Template Modification System scroll horizontal too hard

This is actually a Chrome bug which we've reported to them and has been fixed. I'm not sure what milestone will have the fix though. This applies to any scrollable element with border radius.
The temporary fix is..

ACP > Development > Admin Templates > base_template_modification.css

Change the border-radius to zero in #TemplateContents.

    max-width: 100%;
    border: 1px solid #ccc;
    border-radius: 0; /* workaround for Chrome bug */
    background: #f2f2f2;
    max-height: 250px;
    min-height: 15px;
    overflow: auto;
    white-space: pre;
    word-wrap: normal;
    font-family: Consolas, "Courier New", Courier, monospace;
    direction: ltr;
    padding: 4px;
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