<!DOCTYPE HTML>
<html>
    <head>
        <meta charset="utf-8">
        <title>Test</title>
        <style>
            p {
                width: 150px;
                border: 1px solid black
            }
        </style>
    </head>
    <body>
        <p>Before_&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;_After</p>
    </body>
</html>

Does it have to be a raw, non-breaking space or does the same happen with the entity?

Can you make a minimal test case also?