Problems arise due to the text-rendering property. Text rendering is not a CSS standard, but allows you to use text quality.
In google material css, this property has a default value. If you add this style, you will solve the problem:
.material-icons { text-rendering: optimizeLegibility; }
In this definition, we tell the browser that "emphasize clarity in rendering speed and geometric accuracy."
https://css-tricks.com/almanac/properties/t/text-rendering/
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